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Letteratura scientifica selezionata sul tema "Membranes"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 5 ottobre 2024

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Articoli di riviste sul tema "Membranes"

Abu-Zurayk, Rund, Nour Alnairat, Aya Khalaf, Abed Alqader Ibrahim e Ghada Halaweh. "Cellulose Acetate Membranes: Fouling Types and Antifouling Strategies—A Brief Review". Processes 11, n. 2 (6 febbraio 2023): 489. http://dx.doi.org/10.3390/pr11020489.

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Cellulose acetate (CA) is a semisynthetic, biodegradable polymer. Due to its characteristics, CA has several applications, including water membranes, filament-forming matrices, biomedical nanocomposites, household tools, and photographic films. This review deals with topics related to the CA membranes, which are prepared using different techniques, such as the phase inversion technique. CA membranes are considered very important since they can be used as microfiltration membranes (MF), ultrafiltration membranes (UF), nanofiltration membranes (NF), reverse osmosis (RO) membranes, and forward osmosis (FO) membranes. Membrane fouling results from the accumulation of materials that the membrane rejects on the surface or in the membrane’s pores, lowering the membrane’s flux and rejection rates. There are various forms of CA membrane fouling, for instance, organic, inorganic, particulate fouling, and biofouling. In this review, strategies used for CA membrane antifouling are discussed and summarized into four main techniques: feed solution pretreatment, cleaning of the membrane surface, membrane surface modification, which can be applied using either nanoparticles, polymer reactions, surface grafting, or surface topography, and surface coating.

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Branton, Daniel. "Fracture faces of frozen membranes: 50th anniversary". Molecular Biology of the Cell 27, n. 3 (febbraio 2016): 421–23. http://dx.doi.org/10.1091/mbc.e15-05-0287.

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In 1961, the development of an improved freeze-etching (FE) procedure to prepare rapidly frozen biological cells or tissues for electron microscopy raised two important questions. How does a frozen cell membrane fracture? What do the extensive face views of the cell’s membranes exposed by the fracture process of FE tell us about the overall structure of biological membranes? I discovered that all frozen membranes tend to split along weakly bonded lipid bilayers. Consequently, the fracture process exposes internal membrane faces rather than either of the membrane’s two external surfaces. During etching, when ice is allowed to sublime after fracturing, limited regions of the actual membrane surfaces are revealed. Examination of the fractured faces and etched surfaces provided strong evidence that biological membranes are organized as lipid bilayers with some proteins on the surface and other proteins extending through the bilayer. Membrane splitting made it possible for electron microscopy to show the relative proportion of a membrane’s area that exists in either of these two organizational modes.

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Al Harby, Nouf F., Mervette El-Batouti e Mahmoud M. Elewa. "Prospects of Polymeric Nanocomposite Membranes for Water Purification and Scalability and their Health and Environmental Impacts: A Review". Nanomaterials 12, n. 20 (17 ottobre 2022): 3637. http://dx.doi.org/10.3390/nano12203637.

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Water shortage is a major worldwide issue. Filtration using genuine polymeric membranes demonstrates excellent pollutant separation capabilities; however, polymeric membranes have restricted uses. Nanocomposite membranes, which are produced by integrating nanofillers into polymeric membrane matrices, may increase filtration. Carbon-based nanoparticles and metal/metal oxide nanoparticles have received the greatest attention. We evaluate the antifouling and permeability performance of nanocomposite membranes and their physical and chemical characteristics and compare nanocomposite membranes to bare membranes. Because of the antibacterial characteristics of nanoparticles and the decreased roughness of the membrane, nanocomposite membranes often have greater antifouling properties. They also have better permeability because of the increased porosity and narrower pore size distribution caused by nanofillers. The concentration of nanofillers affects membrane performance, and the appropriate concentration is determined by both the nanoparticles’ characteristics and the membrane’s composition. Higher nanofiller concentrations than the recommended value result in deficient performance owing to nanoparticle aggregation. Despite substantial studies into nanocomposite membrane manufacturing, most past efforts have been restricted to the laboratory scale, and the long-term membrane durability after nanofiller leakage has not been thoroughly examined.

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Ramalho, Maria João, Stéphanie Andrade, Joana Angélica Loureiro e Maria Carmo Pereira. "Interaction of Bortezomib with Cell Membranes Regulates Its Toxicity and Resistance to Therapy". Membranes 12, n. 9 (23 agosto 2022): 823. http://dx.doi.org/10.3390/membranes12090823.

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Bortezomib (BTZ) is a potent proteasome inhibitor currently being used to treat multiple myeloma. However, its high toxicity and resistance to therapy severely limit the treatment outcomes. Drug–membrane interactions have a crucial role in drugs’ behavior in vivo, affecting their bioavailability and pharmacological activity. Additionally, drugs’ toxicity often occurs due to their effects on the cell membranes. Therefore, studying BTZ’s interactions with cell membranes may explain the limitations of its therapy. Due to the cell membranes’ complexity, lipid vesicles were proposed here as biomembrane models, focusing on the membrane’s main constituents. Two models with distinct composition and complexity were used, one composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the other containing DMPC, cholesterol (Chol), and sphingomyelin (SM). BTZ’s interactions with the models were evaluated regarding the drugs’ lipophilicity, preferential location, and effects on the membrane’s physical state. The studies were conducted at different pH values (7.4 and 6.5) to mimic the normal blood circulation and the intestinal environment, respectively. BTZ revealed a high affinity for the membranes, which proved to be dependent on the drug-ionization state and the membrane complexity. Furthermore, BTZ’s interactions with the cell membranes was proven to induce changes in the membrane fluidity. This may be associated with its resistance to therapy, since the activity of efflux transmembrane proteins is dependent on the membrane’s fluidity.

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Romero, Virginia, Lourdes Gelde e Juana Benavente. "Electrochemical Characterization of Charged Membranes from Different Materials and Structures via Membrane Potential Analysis". Membranes 13, n. 8 (17 agosto 2023): 739. http://dx.doi.org/10.3390/membranes13080739.

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Electrochemical characterization of positively and negatively charged membranes is performed by analyzing membrane potential values on the basis of the Teorell–Meyer–Sievers (TMS) model. This analysis allows the separate estimation of Donnan (interfacial effects) and diffusion (differences in ions transport through the membrane) contributions, and it permits the evaluation of the membrane’s effective fixed charge concentration and the transport number of the ions in the membrane. Typical ion-exchange commercial membranes (AMX, Ionics or Nafion) are analyzed, though other experimental and commercial membranes, which are derived from different materials and have diverse structures (dense, swollen or nanoporous structures), are also considered. Moreover, for some membranes, changes associated with different modifications and other effects (concentration gradient or level, solution stirring, etc.) are also analyzed.

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Hong, Sun, Song Hua e Lu Yan. "Preparation and Characterization of Al₂O₃/TiO₂/PVDF Polymer Composites Ultrafiltration Membrane". Applied Mechanics and Materials 253-255 (dicembre 2012): 865–70. http://dx.doi.org/10.4028/www.scientific.net/amm.253-255.865.

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The polymer polyvinylidene fluoride (PVDF) membranes were modified by blending with nanometer particles to improve its hydrophilic property and anti-fouling performances in the process of waste water treatment. The organic macromolecule composite ultrafiltration (UF) membranes modified by the inorganic nanometer TiO2 and Al2O3 were prepared by a phase inversion process. The composite membranes performances, such as water flux, mechanical strength, water contact angle, retention rate, pores size and pores size distribution, were compared to those of organic membranes. The surface and sectional structures of membranes were observed by scanning electron microscope (SEM). The experimental results show that the composite membrane water fluxes increases 79.5% than that of organic membrane with 3% nanometer particles addition and the proportion of TiO2 and Al2O3 is 1:1. The composite membrane average pore size is larger than that of organic membrane and the pore size distribution is more uniform. The composite UF membrane has not only maintained PVDF membrane’s favorable performances but also improved its permeation performance, intensity, hydrophilic and anti-fouling performances.

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Efome, Johnson E., Fan Yang, Dipak Rana, Takeshi Matsuura e Christopher Lan. "Functionalized PVDF Nanofiber Membranes for Desalination by Direct Contact Membrane Distillation". International Journal of Materials Science and Engineering 6, n. 2 (giugno 2018): 67–71. http://dx.doi.org/10.17706/ijmse.2018.6.2.67-71.

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Alshahrani, Ahmed A., Abeer A. El-Habeeb, Arwa A. Almutairi, Dimah A. Almuaither, Sara A. Abudajeen, Hassan M. A. Hassan e Ibrahim Hotan Alsohaimi. "Preparation, Characterization and Evaluation of Polyamide-Reduced Graphene Oxide as Selective Membranes for Water Purification". Journal of Composites Science 8, n. 1 (10 gennaio 2024): 24. http://dx.doi.org/10.3390/jcs8010024.

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Amidst the ongoing advancements in membrane technology, a leading method has come to the forefront. Recent research has emphasized the substantial influence of surface attributes in augmenting the effectiveness of thin-film membranes in water treatments. These studies reveal how surface properties play a crucial role in optimizing the performance of these membranes, further establishing their prominence in the field of membrane technology. This recognition stems from the precise engineering of surfaces, ensuring they meet the demanding requirements of advanced separation processes. This study utilizes polyamide as a discerning layer, applied atop a polysulfone support sheet through interfacial polymerization (IP) for membrane fabrication. The amounts in the various membranes were created to vary. The membrane’s permeability to water with significant salt rejection was enhanced, which improved its effectiveness. The polyamide (PA) membrane comprising graphene oxide (rGO, 0.015%) had a water permeability of 48.90 L/m2 h at 22 bar, which was much higher than the mean permeability of polyamide membranes (25.0 L/m2 h at 22 bar). On the other hand, the PA–rGO/CHIT membranes exhibited the lowest water permeability due to their decreased surface roughness. However, the membranes’ effectiveness in rejecting salts ranged from 80% to 95% for PA–rGO and PA–rGO/CHIT membranes.

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Junoh, Hazlina, Juhana Jaafar, Nik Abdul Hadi Md Nordin, Ahmad Fauzi Ismail, Mohd Hafiz Dzarfan Othman, Mukhlis A. Rahman, Farhana Aziz e Norhaniza Yusof. "Performance of Polymer Electrolyte Membrane for Direct Methanol Fuel Cell Application: Perspective on Morphological Structure". Membranes 10, n. 3 (25 febbraio 2020): 34. http://dx.doi.org/10.3390/membranes10030034.

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Membrane morphology plays a great role in determining the performance of polymer electrolyte membranes (PEMs), especially for direct methanol fuel cell (DMFC) applications. Membrane morphology can be divided into two types, which are dense and porous structures. Membrane fabrication methods have different configurations, including dense, thin and thick, layered, sandwiched and pore-filling membranes. All these types of membranes possess the same densely packed structural morphology, which limits the transportation of protons, even at a low methanol crossover. This paper summarizes our work on the development of PEMs with various structures and architecture that can affect the membrane’s performance, in terms of microstructures and morphologies, for potential applications in DMFCs. An understanding of the transport behavior of protons and methanol within the pores’ limits could give some perspective in the delivery of new porous electrolyte membranes for DMFC applications.

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Yeszhanov, A. B. "HYDROPHOBIZATION OF PET TRACK-ETCHED MEMBRANES FOR DIRECT CONTACT MEMBRANE DISTILLATION OF LIQUID RADIOACTIVE WASTES". Eurasian Physical Technical Journal 17, n. 2 (24 dicembre 2020): 45–54. http://dx.doi.org/10.31489/2020no2/45-54.

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This article provides the results of liquid low-level radioactive wastes treatment by direct contact membrane distillation using polyethylene terephthalate hydrophobic track-etched membranes. The hydrophobization of track-etched membranes was carried out by UV-induced graft polymerization of triethoxyvinylsilane with styrene and coating with fluorine-containing silanes. Hydrophobic membranes were investigated by scanning electron microscope, Fourier-transform infrared spectroscopy, contact anglemeasurements, and liquid entry pressure analysis. Prepared membranes were tested in treatment of liquid low-level radioactive wastes by membrane distillation. The influence of pore sizes on water flux and rejection degree was studied. Rejection degree was evaluated by conductometry and atomic emission method. Decontamination factors evaluated by gamma-ray spectroscopy for 60Co, 137Cs, and 241Am are 85.4, 1900 and 5.4 for membranes modified with polystyrene and triethoxyvinylsilanewith pore diameters of 142 nm; 85.0, 1462 and 4 for membranes modified with perfluorododecyltrichlorosilanewith pore diameters of 150 nm respectively.

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Più fonti

Tesi sul tema "Membranes"

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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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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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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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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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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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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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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Libri sul tema "Membranes"

Basile, Angelo, e Fausto Gallucci, a cura di. Membranes for Membrane Reactors. Chichester, UK: John Wiley & Sons, Ltd, 2011. http://dx.doi.org/10.1002/9780470977569.

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Drioli, Enrico, e Masayuki Nakagaki, a cura di. Membranes and Membrane Processes. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5.

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E, Drioli, e Nakagaki Masayuki 1923-, a cura di. Membranes and membrane processes. New York: Plenum Press, 1986.

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Harris, Maddy Alun, e Harris James R, a cura di. Subcellular Biochemistry. New York: Plenum, 1994.

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H, Maddy A., e Harris J. R, a cura di. Membrane biogenesis. New York: Plenum Press, 1994.

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Graham, J. M. Membrane analysis. Oxford, UK: BIOS Scientific Publishers, 1997.

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Thomas, Tsotsis Theodore, a cura di. Catalytic membranes and membrane reactors. Weinheim: Wiley-VCH, 2002.

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service), SpringerLink (Online, a cura di. Smart Membrane Materials and Systems: From Flat Membranes to Microcapsule Membranes. Berlin, Heidelberg: Zhejiang University Press, Hangzhou and Springer-Verlag Berlin Heidelberg, 2011.

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Jain, Mahendra Kumar. Introduction to biological membranes. 2^a ed. New York: Wiley, 1988.

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Claude, Nicolau, e Chapman Dennis 1927-, a cura di. Horizons in membrane biotechnology: Proceedings of the Third International Meeting on Membrane Biotechnology, held in College Station, Texas, September 17-20, 1989. New York: Wiley-Liss, 1990.

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Capitoli di libri sul tema "Membranes"

Yoshimune, Miki, e Kenji Haraya. "Microporous Carbon Membranes". In Membranes for Membrane Reactors, 63–97. Chichester, UK: John Wiley & Sons, Ltd, 2011. http://dx.doi.org/10.1002/9780470977569.ch1.

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Hori, Ryohei, Ken-ichi Inui, Mikihisa Takano e Tomonobu Okano. "Transport Mechanisms of Organic Ions in Rat Renal Brush Border and Basolateral Membrane Vesicles". In Membranes and Membrane Processes, 1–7. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_1.

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Kimizuka, H., Y. Nagata e W. Yang. "Ion and Solvent Transports Through Amphoteric Ion Exchange Membrane". In Membranes and Membrane Processes, 85–92. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_10.

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Hernandez, A., J. A. Ibañez e A. F. Tejerina. "A Selective Parameter for Ionic Membrane Transport Selectivity and Porosity of Several Passive Membranes". In Membranes and Membrane Processes, 93–99. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_11.

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Lindheimer, A., D. Cros, B. Brun e C. Gavach. "Ionic Permeability of the S18 Saft Carboxylic Membrane". In Membranes and Membrane Processes, 101–13. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_12.

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Strathmann, H. "Preparation of Microporous Membranes by Phase Inversion Processes". In Membranes and Membrane Processes, 115–35. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_13.

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Pittalis, F., e F. Bartoli. "Chitosan Hollow Fibers: Preparation and Properties". In Membranes and Membrane Processes, 137–42. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_14.

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Han, S. J., K. F. Wu, G. X. Wu e Y. B. Wang. "Research on the Preparation of a New Type of Polyarylsulfone Membrane for Ultrafiltration". In Membranes and Membrane Processes, 143–49. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_15.

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Espenan, J. M., e P. Aptel. "Outer Skinned Hollow-Fibers-Spinning and Properties". In Membranes and Membrane Processes, 151–61. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_16.

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Bottino, A., G. Capannelli e S. Munari. "Factors Affecting the Structure and Properties of Asymmetric Polymeric Membranes". In Membranes and Membrane Processes, 163–78. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-2019-5_17.

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Atti di convegni sul tema "Membranes"

Wang, Rong, Chuyang Tang e Tony Fane. "Advances in Membrane Technology: Forward Osmosis/Pressure Retarded Osmosis Membranes and Biomimetic Membranes". In 14th Asia Pacific Confederation of Chemical Engineering Congress. Singapore: Research Publishing Services, 2012. http://dx.doi.org/10.3850/978-981-07-1445-1_596.

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Zhang, Hao, Vishnu Baba Sundaresan, Sergio Salinas e Robert Northcutt. "Electrochemical Analysis of Alamethicin Reconstituted Planar Bilayer Lipid Membranes Supported on Polypyrrole Membranes". In ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5038.

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Conducting polymers possess similarity in ion transport function to cell membranes and perform electro-chemo-mechanical energy conversion. In an in vitro setup, protein-reconstituted bilayer lipid membranes (bioderived membranes)perform similar energy conversion and behave like cell membranes. Inspired by the similarity in ionic function between a conducting polymer membrane and cell membrane, this article presents a thin-film laminated membrane in which alamethicin-reconstituted lipid bilayer membrane is supported on a polypyrrole membrane. Owing to the synthetic and bioderived nature of the components of the membrane, we refer to the laminated membrane as a hybrid bioderived membrane. In this article, we describe the fabrication steps and electrochemical characterization of the hybrid membrane. The fabrication steps include electropolymerization of pyrrole and vesicle fusion to result in a hybrid membrane; and the characterization involves electrical impedance spectroscopy, chronoamperometry and cyclic voltammetry. The resistance and capacitance of BLM have the magnitude of 4.6×109Ω-cm2 and 1.6×10−8 F/cm2.The conductance of alamethicin has the magnitude of 6.4×10−8 S/cm2. The change in ionic conductance of the bioderived membrane is due to the electrical field applied across alamethicin, a voltage-gated protein and produces a measurable change in the ionic concentration of the conducting polymer substrate.

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Bradenburg, Frank. "Architectural Membranes Used for Tensile Membrane Structures". In Structures Congress 2009. Reston, VA: American Society of Civil Engineers, 2009. http://dx.doi.org/10.1061/41031(341)100.

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Sheen, Jyh-Jong, e Shang-Chian Su. "A Pneumatic Micro Peristaltic Pump With Slanted Membranes". In ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2008. http://dx.doi.org/10.1115/icnmm2008-62108.

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We designed and fabricated a bi-directional micro pneumatic peristaltic pump driven by slanted membranes. Unlike most micro peristaltic pumps with discrete polydimethylsiloxane (PDMS) flat membranes, ours has two opposite slanted PDMS membranes tandem along the fluid channel. Since the thickness of the slanted membrane is not uniform, it will produce continuous and asymmetric deflections under increasing pneumatic pressure. The pumping action is achieved by using one membrane as the driving membrane and the other as a stop valve. The flow direction can be controlled by changing phase difference of two driving square waves. Experimental results show that our peristaltic pump achieves much higher maximum flow rate than that of a micro peristaltic pump with three flat membranes of similar size.

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Koombua, Kittisak, Ramana M. Pidaparti, P. Worth Longest e Gary M. Atkinson. "Micropump With Six Vibrating Membranes: Design Analysis". In ASME 2008 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/detc2008-49487.

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In this study, a novel design of multiple vibrating membrane micropump has been investigated. The micropump is composed of six membranes and three nozzle/diffuser elements. The membranes were vibrated out-of-phase simultaneously to create pressure difference in the pump chamber. The characteristics of this micropump were analyzed using the finite volume method. The commercial computational fluid dynamics software, FLUENT, with the dynamic mesh algorithm was employed to study velocity field and flow rate during the operating cycle. The simulation results showed that the movement of these membranes combined with the rectification behavior of three nozzle/diffuser elements can minimize back flow and improve net flow in one direction. The average mass flow rate from the micropump increased when the maximum membrane displacement and membrane frequency increased. However, the average mass flow rate from the micropump decreased when pressure head increased. Increases in maximum pressure head were associated with increases in membrane frequency.

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Romero, T., e W. Me´rida. "Transient Water Transport in Nafion Membranes Under Activity Gradients". In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33317.

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Transient water transport experiments on Nafion of different thicknesses were carried out in the temperature range of 30 to 70 °C. These experiments report on water transport measurements under activity gradients in the time domain for liquid and vapour equilibrated Nafion membranes. Using a permeability test rig with a gated valve, the water crossover was measured as a function of time. The typical response is shown as a time dependent flux, and it shows the dynamic transport from an initially dry condition up to the final steady state. Contrarily to previous reports from dynamic water transport measurements, where the activity gradient across the membrane is absent; in this work, the membrane was subjected to an activity gradient acting as the driving force to transport water from an environment with higher water activity to an environment with lower water activity through the membrane’s structure. Measurements explored temperature and membrane thickness variation effect on the transient response. Results showed dependency on temperature and a slower water transport rate across the vapour-membrane interface than for the liquid-membrane interface. These measurements showed the transport dependency on water content at the beginning of the experiment when the membrane was in a close-to-dry condition suggesting a transport phenomenon transition due to a reached critical water content value. The new protocol for transient measurements proposed here will allow the characterization of water transport dependency on membrane water content with a more rational representation of the membrane-environment interface.

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Saleem, Haleema, e Syed Javaid Zaidi. "Innovative Nanostructured Membranes for Reverse Osmosis Water Desalination". In Qatar University Annual Research Forum & Exhibition. Qatar University Press, 2020. http://dx.doi.org/10.29117/quarfe.2020.0023.

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Reverse osmosis (RO) is considered as the most widely utilized technique worldwide for water treatment. However, the commercial thin-film composite (TFC) membranes, which are normally made of polyamide (PA) through interfacial polymerization (IP), still experience certain major issues in performance and fabrication. The spin assisted layer-by-layer (SA-LbL) technique was established for overcoming some drawbacks with commercially available PA membranes. Also, recent investigations have recognized the nanoparticle inclusion into the selective layer as a powerful technique for improving the membrane efficiency. Hence, two different methodologies are presented here to improve the membrane performance, i.e., (1) SA-LbL technique to fabricate TFC membrane by the deposition of alternate ultrathin layers of different polyelectrolytes on polysulfone (PSF) commercial ultrafiltration membrane and (2) the nanoclay incorporation into the membranes during IP process to develop TFC membrane. Two types of nanoclays, cloisite (CS)-15A and montmorillonite (MNT), were incorporated to enhance the separation efficiency. This SA-LbL is an innovative method for the RO membrane manufacture, and has not been described earlier to the best of our knowledge. In addition, this work validated for the first time, the efficiency of the two nanoclays at the PA selective layer in the RO membrane. The membrane performance was evaluated using sodium chloride solution in a cross-flow permeation-testing cell for salt rejection and water flux. The results show significant improvement in water flux and salt rejection. The permeation test of 120 bilayers of poly (allylaminehydrochloride)/poly (vinylsulfate) on PSF substrate showed water flux of 37 L/ (m2.h) and salt rejection of 53%, for a 2000-ppm salt solution feed. The highest water flux of 40 L/m2.h with 80% salt rejection, relative to the control membrane was obtained for the membranes containing nanoclays at 25oC temperature, 40.0 bar pressure and 2000 ppm feed concentration. Thus, our study demonstrated that these TFC membranes are promising, and these novel fabrication techniques are great tool to manufacture the RO membrane.

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Mateus, Marilia, Luis Raiado-Pereira e Miguel Prazeres. "Membrane chromatography for therapeutic DNA production: Adsorption membranes development". In 2011 1st Portuguese Meeting in Bioengineering ¿ The Challenge of the XXI Century (ENBENG). IEEE, 2011. http://dx.doi.org/10.1109/enbeng.2011.6026054.

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Soares, T. A., T. P. Straatsma, Theodore E. Simos e George Maroulis. "Towards Simulations of Outer Membrane Proteins in Lipopolysaccharide Membranes". In COMPUTATIONAL METHODS IN SCIENCE AND ENGINEERING: Theory and Computation: Old Problems and New Challenges. Lectures Presented at the International Conference on Computational Methods in Science and Engineering 2007 (ICCMSE 2007): VOLUME 1. AIP, 2007. http://dx.doi.org/10.1063/1.2836008.

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Emori, Kanako, Akio Yonezu, Takumi Nagakura e Tatsuma Miura. "Anisotropic Deformation Behavior of Porous Polymeric Membranes Under Uni-Axial and Bi-Axial Loadings". In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11099.

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Abstract This study systematically investigates the uniaxial and biaxial tensile deformation behavior of polytetrafluoroethylene (PTFE) membranes which are used for water purification. The present PTFE membrane has micron size pores with open cell structure, and the pore is anisotropic shape. During the uniaxial tensile test, the membranes undergo elastic deformation and plastic deformation with strain rate sensitivity (i.e. time-dependent deformation behavior). In addition, it strongly demonstrates anisotropic deformation, i.e. deformation behavior is different along longitudinal direction and transverse ones. To clarify the microscopic deformation mechanism, in-situ SEM observation is carried out during tensile loading. It is found that the anisotropic deformation behavior appears due to the inherent pore structure. Next, to investigate deformation behavior under biaxial loading condition, small punch test using a spherical indenter is carried out. The membrane undergoes elastic and plastic deformations. Finally, crack nucleates around the indenter contact and indenter completely penetrates through the membrane. It is also found that the membrane demonstrates anisotropic out-of-plane deformation behavior. To clarify these mechanisms, FEM computation is carried out, such that experimental results of force-displacement curve and out-of-plane deformation behavior are compared with the computational ones. The present FEM model enables the prediction of the membrane’s deformation behavior under biaxial loading.

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Rapporti di organizzazioni sul tema "Membranes"

Husson, Scott M., Viatcheslav Freger e Moshe Herzberg. Antimicrobial and fouling-resistant membranes for treatment of agricultural and municipal wastewater. United States Department of Agriculture, gennaio 2013. http://dx.doi.org/10.32747/2013.7598151.bard.

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This research project introduced a novel membrane coating strategy to combat biofouling, which is a major problem for the membrane-based treatment of agricultural and municipal wastewaters. The novelty of the strategy is that the membrane coatings have the unique ability to switch reversibly between passive (antifouling) and active (antimicrobial) fouling control mechanisms. This dual-mode approach differs fundamentally from other coating strategies that rely solely on one mode of fouling control. The research project had two complementary objectives: (1) preparation, characterization, and testing of dual-mode polymer nanolayers on planar surfaces and (2) evaluation of these nanolayers as membrane modifiers. The first objective was designed to provide a fundamental understanding of how polymer nanolayer chemistry and structure affect bacterial deposition and to demonstrate the reversibility of chemical switching. The second objective, which focused on membrane development, characterization, and testing, was designed to demonstrate methods for the production of water treatment membranes that couple passive and active biofouling control mechanisms. Both objectives were attained through synergistic collaboration among the three research groups. Using planar silicon and glass surfaces, we demonstrated using infrared spectroscopy that this new polymer coating can switch reversibly between the anti-fouling, zwitterion mode and an anti-microbial, quaternary amine mode. We showed that switching could be done more than 50 times without loss of activity and that the kinetics for switching from a low fouling zwitterion surface to an antimicrobial quaternary amine surface is practical for use. While a low pH was required for switching in the original polymer, we illustrated that by slightly altering the chemistry, it is possible to adjust the pH at which the switching occurs. A method was developed for applying the new zwitterionic surface chemistry onto polyethersulfone (PES) ultrafiltration membranes. Bacteria deposition studies showed that the new chemistry performed better than other common anti-fouling chemistries. Biofilm studies showed that PESultrafiltration membranes coated with the new chemistry accumulated half the biomass volume as unmodified membranes. Biofilm studies also showed that PES membranes coated with the new chemistry in the anti-microbial mode attained higher biofilm mortality than PES membranes coated with a common, non-switchablezwitterionic polymer. Results from our research are expected to improve membrane performance for the purification of wastewaters prior to use in irrigation. Since reduction in flux due to biofouling is one of the largest costs associated with membrane processes in water treatment, using dual-mode nanolayer coatings that switch between passive and active control of biofouling and enable detachment of attached biofoulants would have significant economic and societal impacts. Specifically, this research program developed and tested advanced ultrafiltration membranes for the treatment of wastewaters. Such membranes could find use in membrane bioreactors treating municipal wastewater, a slightly upgraded version of what presently is used in Israel for irrigation. They also may find use for pretreatment of agricultural wastewaters, e.g., rendering facility wastewater, prior to reverse osmosis for desalination. The need to desalinate such impaired waters water for unlimited agricultural use is likely in the near future.

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Brown, Ashleigh. Mucous membranes. Brooke, novembre 2020. http://dx.doi.org/10.46746/gaw.2020.abi.memb.

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Buxbaum, Robert. High Flux Metallic Membranes for Hydrogen Recovery and Membrane Reactors. Office of Scientific and Technical Information (OSTI), giugno 2010. http://dx.doi.org/10.2172/1126695.

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EVANS, LINDSEY, e JAMES E. MILLER. Sweeping Gas Membrane Desalination Using Commercial Hydrophobic Hollow Fiber Membranes. Office of Scientific and Technical Information (OSTI), gennaio 2002. http://dx.doi.org/10.2172/793312.

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Frederick F Stewart. NHI-Acid Concentration Membranes -- Membrane Recommendations for the S-I Cycle. Office of Scientific and Technical Information (OSTI), marzo 2007. http://dx.doi.org/10.2172/915523.

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Zhanchun Tu, Zhanchun Tu. Geometry of Membranes. Journal of Geometry and Symmetry in Physics, 2012. http://dx.doi.org/10.7546/jgsp-24-2011-45-75.

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S. Bandopadhyay. Oxygen Transport Membranes. Office of Scientific and Technical Information (OSTI), agosto 2008. http://dx.doi.org/10.2172/940905.

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Anderson, M. A., C. G. Jr Hill e W. A. Zeltner. Ordered ceramic membranes. Office of Scientific and Technical Information (OSTI), ottobre 1991. http://dx.doi.org/10.2172/6231985.

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Donald P. McCollor e John P. Kay. HYDROGEN SEPARATION MEMBRANES. Office of Scientific and Technical Information (OSTI), agosto 1999. http://dx.doi.org/10.2172/778449.

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Michl, Josef, e Thomas Magnera. Molecular Grid Membranes. Fort Belvoir, VA: Defense Technical Information Center, marzo 2008. http://dx.doi.org/10.21236/ada482361.

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