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Biorreatores com membranas : uma alternativa para o tratamento de efluentes

Silva, Maurício Kipper da
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
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A integração da tecnologia de separação por membrana em processos convencionais de lodos ativados representa uma inovação importante na evolução da tecnologia de tratamento biológico de efluentes. Este trabalho tem como objetivo avaliar o desempenho de um biorreator com membranas submersas, provido de um sistema de retrolavagem das membranas, utilizado para o tratamento contínuo de um efluente sintético. As membranas utilizadas foram do tipo fibras ocas e fabricadas do material poli(éter-imida). Foram testadas diferentes condições de aeração e freqüências de retrolavagens. Em todas as condições testadas foi observado o decréscimo contínuo e acentuado do fluxo permeado com o decorrer do tempo, com fluxos permeados finais aproximados de 10 L.m-2.h-1, e o sistema de biorreator com membranas aparenta não responder de forma adequada aos métodos de controle do fouling. Os experimentos mais longos, 80 horas de duração, apresentaram um decréscimo de 50% do fluxo permeado inicial nas melhores condições experimentais testadas, não sendo observado um estado estacionário para o fluxo permeado. Foi verificado que as características do efluente sintético (a base de soro de leite) têm influência na formação do fouling...

Avaliações térmica e reológica da matriz termoplástica PEKK utilizada em compósitos aeronáuticos

Mazur, Rogério L.; Botelho, Edson Cocchieri; Costa, Michelle L.; Rezende, Mirabel C.
Fonte: Associação Brasileira de Polímeros Publicador: Associação Brasileira de Polímeros
Tipo: Artigo de Revista Científica Formato: 237-243
POR
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); A matriz termoplástica semicristalina PEKK (poli (éter-cetona-cetona)) tem recebido nos últimos anos uma atenção crescente pelas indústrias aeronáutica e espacial, no processamento de compósitos poliméricos avançados. As características de elevados valores de temperatura de transição vítrea, de resistência mecânica e de módulo de elasticidade, baixa absorção de umidade, excelente resistência a variações de condições climáticas, combinadas a uma relativa baixa massa específica faz do PEKK uma atrativa opção para uma variedade de aplicações, principalmente na área aeronáutica. O objetivo deste trabalho é correlacionar parâmetros térmicos e reológicos do PEKK, por meio das técnicas de calorimetria exploratória diferencial (DSC), termogravimetria (TG) e reológica, no estabelecimento de um ciclo térmico de processamento, a ser utilizado na obtenção de laminados de PEKK com fibras de carbono, pela técnica de moldagem por compressão a quente de compósitos termoplásticos. Os resultados obtidos mostram que o PEKK apresenta um excelente balanço de propriedades...

The Effect of Water Immersion and UV Radiation Aging on the Shear Behavior of Woven Continuous Fiber/PEI Laminates

Ribeiro, B.; Botelho, Edson Cocchieri; Rezende, M. C.; Costa, M. L.
Fonte: Sampe Publishers Publicador: Sampe Publishers
Tipo: Artigo de Revista Científica
ENG
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 05/54358-7; Processo FAPESP: 08/00171-1; The hygrothermal and UV radiation influences on shear properties and moisture diffusion aging in polyetherimide (PEI) reinforced with continuous fibers were systematically studied in this research, by using ILSS and losipescu shear tests. The moisture weight gain curves of the PEI composites reinforced with glass fiber and carbon fiber were compared in order to determine the interface effect on moisture absorption. Both composites display similar anomalous diffusion behavior; the PEI reinforced with glass fiber presented higher diffusion and water absorption values. The mechanical results indicate that moisture associated with temperature and UV radiation degrades the shear properties by about 20%, giving evidences of plasticization of PEI matrix.

Compósitos poliméricos de poli (éter imida)/polianilina : preparação e caracterização; Polymer composites of poly (ether imide) polyaniline : preparation and characterization

Evandro Mendes Alexandrino
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/02/2012 PT
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A combinação de polianilina (PAni) com termoplásticos, elastômeros e termorrígidos na forma de compósitos e blendas tem sido amplamente estudada nas últimas duas décadas. Entretanto, a utilização de termoplásticos de alto desempenho térmico em compósitos ou blendas com polianilina tem sido pouco explorada devido às altas temperaturas de processamento destes termoplásticos e no fato de que, nestas condições, a PAni se apresenta termicamente instável de acordo com a natureza do dopante utilizado. A poli(éter imida) (PEI) é um termoplástico de engenharia que apresenta boas propriedades térmicas e mecânicas, porém apresenta altas temperaturas de processamento. Nesta dissertação de Mestrado, PAni foi sintetizada em escala laboratorial através de oxidação química, gerando a PAni dopada com ácido clorídrico (PAni HCl). A PAni HCl foi desdopada e redopada para obtenção de PAni dopada com ácido p-tolueno sulfônico (PAni APTS) ou com um complexo de cobalto com acetonitrila (PAni CoAcn). Foram preparados compósitos de PEI com PAni APTS, com teor de PAni entre 2,5 a 20% em massa, por extrusão em uma mini-extrusora dupla rosca. Compósitos de PEI plastificada (PEIR) com resorcinol bis(difenil fosfato) (RDP) também foram preparados com PAni APTS ou PAni CoAcn...

Study and optimization of aroma recovery from beer by pervaporation

Margarida Catarino; António Ferreira; Adélio Mendes
Fonte: Universidade do Porto Publicador: Universidade do Porto
Tipo: Artigo de Revista Científica
ENG
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This work studies the aroma extraction from beer by pervaporation, using a polyoctylmethylsiloxane/polyetherimide (POMS/PEI) composite asymmetric membrane. A response surface methodology (RSM) was used to describe the influence of the operating conditions (factors) on process performance. The factors considered for the design of experiments were the feed temperature, the feed velocity and the permeate pressure. The responses considered were the permeate flux, the aromas/ethanol selectivities, the ethanol concentration and the ratio between high alcohols and esters concentrations on the permeate. It was concluded that the membrane flux increases with the temperature and cross feed velocity while it decreases with permeate pressure. The aroma selectivities are affected by the operating conditions according to their nature. RSM methods generated interpolating polynomial models that describe the relationship between the operating conditions and process responses. A good agreement between experimental and predicted values was observed. The optimal operating conditions were achieved using an objective function that weights the selected responses desirability. The optimal operating conditions were 12.4 °C for feed temperature, 0.45 m s -1 for feed velocity and 1.0 mbara for permeate pressure. For these conditions the permeate flux was predicted to be 7.26 kg m -2 s -1; the high alcohols selectivity ranged from 1.31 to 3.39; the esters selectivity ranged from 14.46 to 17.10 and the high alcohols/esters ratio was predicted to be 1.07. Experimental results for the runs performed at the optimal operating conditions mostly agreed with the predicted values.

Polyimide and polyetherimide organic solvent nanofiltration membranes

Silva, Marta Sofia Fragoso da
Fonte: FCT - UNL Publicador: FCT - UNL
Tipo: Dissertação de Mestrado
Publicado em //2007 ENG
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Integrally asymmetric skinned Lenzing P84 and Matrimid 5218 polymide membranes and Ultem 1000 polyetherimide membranes were prepared. Crosslinking of membranes using aliphatic diamines resulted in marked improvement in chemical stability. This however resulted in a decline in flux with only Lenzing P84 demonstrating good flux in DMF. Further variation of membrane dope parameters and operating conditions allowed for good control of the MWCO of membranes made from Lenzing P84. SEM pictures of Lenzing P84 membranes revealed a significant difference in membranes morphology. The presence of macrovoids increased when using more DMF in the dope solution. These studies demonstrate the possibility of developing OSN membranes using different polyimides and opens up future possibilities for controlling the MWCO of these membranes. Preliminary modelling demonstrates that good control of the MWCO could extend the application of OSN membranes to allow the fraction of molecules in the NF range.

LIPASE IMMOBILIZED MEMBRANE REACTOR APPLIED TO BABASSU OIL HYDROLYSIS

Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/1997 EN
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This work deals with enzymatic hydrolysis of babassu oil by immobilized lipase in membrane reactors of two types: a flat plate nylon membrane and a hollow fiber polyetherimide membrane on which surface commercial lipases were immobilized by adsorption. Experiments conducted in the hollow fiber reactor showed that during the immobilization step enzyme adsorption followed a sigmoid model, with a maximum adsorption equilibrium time of 30 minutes. Concerning the hydrodynamics of the liquid phases, the results indicate that main diffusional limitations occurred in the organic phase. The amount of protein immobilized and the maximum productivity were, respectively, 1.97 g/m2 and 44 m molH+/m2.s for the hollow fiber and 1.2 g/m2 and 56 m molH+/m2.s for the flat and plate membrane. Both reactors were able to perform the hydrolysis reaction, while maintaining absolute separation of the two phases by the membrane

Developing the dielectric mechanisms of polyetherimide/multiwalled carbon nanotube/(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 composites

Su, Chean-Cheng; Wu, Chia-Ching; Yang, Cheng-Fu
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 16/02/2012 EN
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Various amounts of multiwalled carbon nanotubes [MWNTs] were embedded into polyetherimide [PEI] to form PEI/MWNT composites, and their dielectric properties were measured at 1 MHz. The Lichtenecker mixing rule was used to find a reasonable dielectric constant for the MWNTs used in this study. The dielectric constants of the developed composites were significantly increased, and the loss tangents were significantly decreased as 2.0 wt.% (Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 ceramic powder [BSTZ] was added to the PEI/MWNTs to form PEI/MWNT/BSTZ composites. The Lichtenecker and Yamada mixing rules were used to predict the dielectric constants of the PEI/MWNT and PEI/MWNT/BSTZ composites. Equivalent electrical conduction models of both composites were established using the two mixing rules. In addition, the theoretical bases of the two mixing rules were used to explain the measured results for the PEI/MWNT and PEI/BSTZ/MWNT composites.

On the Evaluation of the Elastic Modulus of Soft Materials Using Beams with Unknown Initial Curvature

Khatam, Hamed; Ravi-Chandar, K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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A nonlinear optimization procedure is established to determine the elastic modulus of slender, soft materials using beams with unknown initial curvature in the presence of large rotations. Specifically, the deflection of clamped-free beams under self-weight – measured at different orientations with respect to gravity – is used to determine the modulus of elasticity and the intrinsic curvature in the unloaded state. The approach is validated with experiments on a number of different materials – steel, polyetherimide, rubber and pig skin. Since the loading is limited to self-weight, the strain levels attained in these tests are small enough to assume a linear elastic material behavior. This nondestructive methodology is also applicable to engineered tissues and extremely delicate materials in order to obtain a quick estimate of the material’s elastic modulus.

The Surface Charge and Cellular Processing of Covalently Functionalized Multiwall Carbon Nanotubes Determine Pulmonary Toxicity

Li, Ruibin; Wang, Xiang; Ji, Zhaoxia; Sun, Bingbing; Zhang, Haiyuan; Chang, Chong Hyun; Lin, Sijie; Meng, Huan; Liao, Yu-Pei; Wang, Meiying; Li, Zongxi; Hwang, Angela; Song, Tze-Bin; Xu, Run; Yang, Yang; Zink, Jeffrey I.; Nel, André E.; Xia, Tian
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Functionalized carbon nanotubes (f-CNTs) are being produced in increased volume because of the ease of dispersion and maintenance of the pristine material physicochemical properties when used in composite materials as well as for other commercial applications. However, the potential adverse effects of f-CNTs have not been quantitatively or systematically explored, and in this study we used a library of covalently functionalized multiwall carbon nanotubes (f-MWCNTs), established from the same starting material, to assess the impact of surface charge in a predictive toxicological model that relates the tubes’ pro-inflammatory and pro-fibrogenic effects at cellular level to the development of pulmonary fibrosis. Carboxylated (COOH), polyethylene glycol (PEG), amine (NH2), sidewall amine (sw-NH2) and polyetherimide (PEI) modified MWCNTs were successfully established from raw or as-prepared (AP-) MWCNTs, and comprehensively characterized by TEM, XPS, FTIR and DLS to obtain information about morphology, length, degree of functionalization, hydrodynamic size and surface charge. Cellular screening in BEAS-2B and THP-1 cells showed that, compared to AP-MWCNTs, anionic functionalization (COOH and PEG) decreased the production of pro-fibrogenic cytokines and growth factors (including IL-1β...

Thermodynamics of water sorption in high performance glassy thermoplastic polymers

Scherillo, Giuseppe; Petretta, Mauro; Galizia, Michele; La Manna, Pietro; Musto, Pellegrino; Mensitieri, Giuseppe
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 14/05/2014 EN
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Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging from 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different “populations” of water molecules present within the PEEK and a quantitative assessment of these “populations” in the case of PEI. The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non-equilibrium nature of glassy polymers as well as for mean field and for hydrogen bonding interactions...

Preparation of bufalin-loaded pluronic polyetherimide nanoparticles, cellular uptake, distribution, and effect on colorectal cancer

Hu, Qiang; Liang, Bo; Sun, Ying; Guo, Xiao-Ling; Bao, Yi-Jie; Xie, Dong-Hao; Zhou, Ming; Duan, You-Rong; Yin, Pei-Hao; Peng, Zhi-Hai
Fonte: Dove Medical Press Publicador: Dove Medical Press
Tipo: Artigo de Revista Científica
Publicado em 21/08/2014 EN
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A large number of studies have shown that bufalin can have a significant antitumor effect in a variety of tumors. However, because of toxicity, insolubility in water, fast metabolism, short half-life, and other shortcomings, its application is limited in cancer therapy. In this study, we explored the anti-metastatic role of bufalin-loaded pluronic polyetherimide nanoparticles on HCT116 colon cancer-bearing mice. Nanoparticle size, shape, drug loading, encapsulation efficiency, and in vitro drug release were studied. Also, cellular uptake of nanoparticles, in vivo tumor targeting, and tumor metastasis were studied. The nanoparticles had a particle size of about 60 nm and an encapsulation efficiency of 75.71%, by weight. The in vitro release data showed that free bufalin was released faster than bufalin-loaded pluronic polyetherimide nanoparticles, and almost 80% of free bufalin was released after 32 hours. Nanoparticles had an even size distribution, were stable, and had a slow release and a tumor-targeting effect. Bufalin-loaded pluronic polyetherimide nanoparticles can significantly inhibit the growth and metastasis of colorectal cancer.

Polyetherimide-grafted Fe3O4@SiO2 nanoparticles as theranostic agents for simultaneous VEGF siRNA delivery and magnetic resonance cell imaging

Li, Tingting; Shen, Xue; Chen, Yin; Zhang, Chengchen; Yan, Jie; Yang, Hong; Wu, Chunhui; Zeng, Hongjun; Liu, Yiyao
Fonte: Dove Medical Press Publicador: Dove Medical Press
Tipo: Artigo de Revista Científica
Publicado em 02/07/2015 EN
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Engineering a safe and high-efficiency delivery system for efficient RNA interference is critical for successful gene therapy. In this study, we designed a novel nanocarrier system of polyethyleneimine (PEI)-modified Fe3O4@SiO2, which allows high efficient loading of VEGF small hairpin (sh)RNA to form Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites for VEGF gene silencing as well as magnetic resonance (MR) imaging. The size, morphology, particle stability, magnetic properties, and gene-binding capacity and protection were determined. Low cytotoxicity and hemolyticity against human red blood cells showed the excellent biocompatibility of the multifunctional nanocomposites, and also no significant coagulation was observed. The nanocomposites maintain their superparamagnetic property at room temperature and no appreciable change in magnetism, even after PEI modification. The qualitative and quantitative analysis of cellular internalization into MCF-7 human breast cancer cells by Prussian blue staining and inductively coupled plasma atomic emission spectroscopy analysis, respectively, demonstrated that the Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites could be easily internalized by MCF-7 cells, and they exhibited significant inhibition of VEGF gene expression. Furthermore...

Positive pressure drop-on-demand printhead for Three-Dimensional Printing

Gleason, Blake Wilbur
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 98 leaves:; 5043920 bytes; 5048917 bytes; application/pdf; application/pdf
ENG
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In drop-on-demand printing, wetting out of the binder fluid onto the orifice face typically has been prevented by some combination of the following: coatings on the orifice face, high surface energy fluids, and negative pressure. This non-wetting approach is not practical for low surface energy fluids. A new positive pressure method of drop-on-demand printing has been developed which eliminates the requirement for a non-wetting system; modifications to the binder fluid properties or to the orifice material to ensure non-wetting are no longer necessary for reliable drop formation. In fact, slight positive pressure (relative to atmosphere) is maintained in the binder fluid at the orifice to achieve intentional wetting of a small area around the orifice. The pressure causes the binder meniscus to bulge out from the orifice until it detaches from the orifice edge and wets the orifice face. The binder wetting continues outward from the orifice edge along the plane of the orifice face, and would continue uncontrolled were it not for an additional constraint: the orifice face ends abruptly with a sharp corner to which the meniscus attaches, thus defining the wetting boundary for the binder. With such a boundary in place, the fluid meniscus forms a spherical cap on the orifice face. The thickness of the cap can be varied by adjusting the level of positive pressure. Benefits of this controlled wetting include successful drop-on-demand printing with low surface energy fluids...

Clarificação de suco de maracujá por microfiltração: análise experimental e modelagem matemática

Domingues, Rui Carlos Castro
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
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O maracujá amarelo (Passiflora edulis) é comercializado mundialmente e o Brasil é o maior produtor mundial, sendo que cerca de 95% de sua produção voltada para o mercado de bebidas. O processamento convencional de sucos de frutas envolve diversas etapas em batelada, envolvendo uma grande demanda de tempo e recursos energéticos. Processos de separação com membranas podem ser utilizados para a remoção de micro-organismos, sem que o suco seja submetido a tratamentos térmicos indesejados, possibilitando a obtenção de uma polpa concentrada e fibrosa e uma fração clarificada e esterilizada, conservando suas propriedades sensoriais. Neste trabalho foram estudados procedimentos de pré-tratamento da polpa de maracujá antes da microfiltração, como a centrifugação, tratamento enzimático e de pré-clarificação com quitosana. Foi avaliado o efeito da combinação destes pré-tratamentos nas características físico-químicas da polpa de maracujá, bem como o seu efeito no fluxo de permeado durante a microfiltração. Foi estudado o efeito da pressão transmembrana (PTM) no fluxo de permeado e as características físico-químicas do mesmo. Depois de levantados os dados experimentais de fluxo de permeado, foi aplicado o modelo matemático proposto por FIELD et al. (1995) para se efetuar a descrição dos mecanismos de fouling ocorridos. Foi utilizado um módulo de microfiltração...

Integração de processos físico-químicos e oxidativos avançados no tratamento de efluentes da indústria de laticínios; Integration of physicochemical and advanced oxidation process in treatment of dairy industry wastewater

Mendes, Paulo Ricardo Amador
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/04/2014 PT
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Por meio das mudanças de paradigmas relacionados à gestão ambiental e elevação dos custos de lançamento de efluente, captação e tratamento de água, as indústrias passam por processos de inovação que resultam em melhor utilização dos recursos e maior diminuição dos custos. Além disso, as empresas estão sujeitas a maiores exigências quanto à legislação ambiental vigente impulsionando-as a implantar sistemas de reúso de efluentes. Apesar de representar uma importante atividade econômica, a indústria de laticínios é responsável pela geração de efluentes líquidos com alto potencial poluidor. O presente trabalho teve como objetivo a redução de contaminantes e melhoria da biodegradabilidade de efluentes de laticínios utilizando tratamentos combinados, em destaque, coagulação/floculação, processos com membranas e oxidação/redução química fotocatalítica. Os efluentes foram provenientes de uma indústria da região, oriundos da etapa de nanofiltração do soro ultrafiltrado. Eles foram divididos em duas correntes, denominadas de concentrado de nanofiltração (corrente 1) e permeado de nanofiltração (corrente 2). Para o tratamento da corrente 1 foi proposto inicialmente coagulação/floculação utilizando diferentes agentes coagulantes naturais (quitosana...

Multifunctional Core/Shell Nanoparticles Cross-linked Polyetherimide-folic Acid as Efficient Notch-1 siRNA Carrier for Targeted Killing of Breast Cancer

Yang, Hong; Li, Ying; Li, Tingting; Xu, Min; Chen, Yin; Wu, Chunhui; Dang, Xitong; Liu, Yiyao
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 17/11/2014 EN
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In gene therapy, how genetic therapeutics can be efficiently and safely delivered into target tissues/cells remains a major obstacle to overcome. To address this issue, nanoparticles consisting of non-covalently coupled polyethyleneimine (PEI) and folic acid (FA) to the magnetic and fluorescent core/shell of Fe3O4@SiO2(FITC) was tested for their ability to deliver Notch-1 shRNA. Our results showed that Fe3O4@SiO2(FITC)/PEI-FA/Notch-1 shRNA nanoparticles are 64 nm in diameter with well dispersed and superparamagnetic. These nanoparticles with on significant cytotoxicity are capable of delivering Notch-1 shRNA into human breast cancer MDA-MB-231 cells with high efficiency while effectively protected shRNA from degradation by exogenous DNaseI and nucleases. Magnetic resonance (MR) imaging and fluorescence microscopy showed significant preferential uptake of Fe3O4@SiO2(FITC)/PEI-FA/Notch-1 shRNA nanocomplex by MDA-MB-231 cells. Transfected MDA-MB-231 cells exhibited significantly decreased expression of Notch-1, inhibited cell proliferation, and increased cell apoptosis, leading to the killing of MDA-MB-231 cells. In light of the magnetic targeting capabilities of Fe3O4@SiO2(FITC)/PEI-FA, our results show that by complexing with a second molecular targeting therapeutic...

Sublinear dispersive conductivity in polyetherimides by the electric modulus formalism

Mudarra, M.; Sellares, J.; Canadas, J. C.; Diego, J. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/07/2013
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It can be seen by Dynamic Electrical Analysis that the electrical properties of polyetherimide at temperatures above the glass transition are strongly influenced by space charge. We have studied space charge relaxation in two commercial grades of polyetherimide, Ultem 1000 and Ultem 5000, using this technique. The electric modulus formalism has been used to interpret their conductive properties. In both grades of polyetherimide, asymmetric Argand plots are observed, which are related to a sublinear power-law dependency ($\omega^{n}$ with $n<1$) in the real part of the conductivity. This behaviour is attributed to correlated ion hopping. The imaginary part of the electric modulus exhibits a peak in the low frequency range associated to conduction. Modelling of this peak allows us to obtain the dependence, among other parameters, of the conductivity ($\sigma_0$), the fractional exponent ($n$) and the crossover frequency ($\omega_\mathrm{p}$) on the temperature. The $\alpha$ relaxation, that appears at higher frequencies, has also to be modelled since it overlaps the conductivity relaxation. The study of the parameters in terms of the temperature allows us to identify the ones that are thermally activated. The difference between the conductivity relaxation time and the Maxwell relaxation time indicates the presence of deep traps. The coupling model points out that the correlation of the ionic motion diminishes with temperature...

Electrical properties of polyetherimide thin films: Nonparametric dielectric reponse analysis with distribution of relaxation times

Tuncer, Enis
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 19/04/2013
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High temperature polymeric materials for electrical insulation and energy storage are needed for transformational power applications such as pulsed-power and hyrid electrical vehicles. One of the candidate materials has been polyetherimide, an amourphous thermoplastic with a glass transition over 200C. Here dielectric studies on the material are reported by taking into account the polarization and conduction processes in the polyetherimide.