检索结果-南通市图书馆

The Development and Characterization of Polycaprolactone and Titanium Dioxide Hybrids

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Advances in Nanoparticles 2018年第1期7卷 11-27页

作者： mariana sato de s. b. Monteiro maria inês b.uno tavares Faculdade de Farmácia Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil Instituto de Macromoléculas Professora Eloísa Mano Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil

Organic/Inorganic hybrid materials have been attracting much attention since they combine the advantages of inorganic materials with the properties of organic polymers. Titanium dioxide nanoparticles (TiO2) present good thermal stability, accessibility and catalytic properties. Polycaprolactone (PCL) is a bi-ocompatible and bioresorbable material, which is being examined as biode-gradable packaging materials, controlled drug release carriers and other medical applications. Hybrids based on PCL containing different amounts of titanium dioxide nanoparticles, ranging from 0.05% to 0.35% w/w, were prepared using the solution cast method. These systems were characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), low-field nuclear magnetic resonance (NMR), thermogravimetric analysis (TG) and differential scanning calorimetry (DsC). The FTIR analysis confirmed that there was an interaction between the PCL chains and the TiO2 nanoparticles. The XRD and DsC analysis showed that the PCL crystallization was affected by TiO2 incorporation, modifying its semi-crystalline structure to a less ordered structure. When TiO2 nanoparticles were added the values of T1H and T1ρH increased for all hybrids, therefore, their addition produced a new material with less molecular mobility. In the TG analysis, it was observed that the introduction of TiO2 nanoparticles decreased the thermal resistance of PCL. In DsC analysis, the PCL/TiO2 hybrids presented a reduction in the crystallization temperature and degree of crystallinity, except for PCL hybrids containing 0.15% w/w of TiO2 nanoparticles.

关键词： Poly (ε -Caprolactone) Dioxide Titanium Hybrids NMR Relaxometry

PLA-starch Microparticles Containing Clays Focusing Controlled Release of Rifampicin

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Materials sciences and Applications 2022年第7期13卷 441-452页

作者： Luciana Macedo brito maria inês b.uno tavares Universidade Federal Rural do Rio de Janeiro Campus Universitário-Seropédica Rio de Janeiro-RJ Brazil Instituto de Macromoléculas Professora Eloisa Mano da Universidade Federal do Rio de Janeiro (IMA/UFRJ) Centro de Tecnologia Ilha do Fund&atilde o Rio de Janeiro RJ Brazil

Polymer nanocomposites have been successfully used as excipients in pharmaceutical technology because of the convenient features that make them suitable for many applications, especially in controlled drug delivery therapies. The objective of this work was to prepare and characterize PLA and starch microparticles containing Viscogel b8 organophilic clay as a matrix for controlled release of rifampicin, one of the most spread drugs for tuberculosis treatment. The systems obtained by the spray drying technique were characterized by DRX, FTIR, sEM and low-field NMR. In addition, dissolution tests were performed on simulated gastric fluid. The micrographs indicate that the presence of the drug caused a small change in the shape and size of the particles. In the presence of the drug, the particles were spherical and presented wider size distribution. The XRD assays didn’t show crystalline peaks of rifampicin in the microparticles, which suggests that rifampicin exists in an amorphous solid solution inside the starch-PLA particles. The mathematical model of baker-Lonsdale was chosen for the treatment of the dissolution data, describing the controlled release of the drug from the matrix by a spherical diffusion process. The results suggest that the proposed release system may be used for the delivery of orally administered drugs, such as rifampicin.

关键词： PLA starch Drug Release Nanotechnology

Increasing Powers in a Degenerate Parabolic Logistic Equation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Annals of Mathematics,series b 2013年第2期34卷 277-294页

作者： Jos Francisco RODRIGUEs Hugo tavares Department of Mathematics and CMAF Universidade de LisboaAvenida Professor Gama Pinto 21649-003 LisboaPortugal

The purpose of this paper is to study the asymptotic behavior of the positive solutions of the problem tu- △u=au-b（x）up in Ω×R＋,u（0）=u0,u（t ）｜ Ω=0, as p→ ＋∞, where Ω is a bounded domain, and b（x） is a nonnegative function. The authors deduce that the limiting configuration solves a parabolic obstacle problem, and afterwards fully describe its long time behavior.

关键词： Parabolic logistic equation Obstacle problem Positive solution Increasing power subsolution and supersolution

Development of Polycaprolactone/Poly(Vinyl Alcohol)/Clay Microparticles by spray Drying

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Materials sciences and Applications 2016年第10期7卷 575-592页

作者： mariana sato de s. de b. Monteiro Claudia Lopes Rodrigues Eduardo Miguez maria Inês b. tavares Instituto de Macromoléculas Professora Eloisa Universidade Federal do Rio de Janeiro Centro de Tecnologia Bloco J Cidade Universitária Ilha do Fundao Rio de Janeiro Brazil Faculdade de Farmácia Universidade Federal do Rio de Janeiro Centro de Ciências da Saúde Bloco L Cidade Universitária Ilha do Fundao Rio de Janeiro Brazil

In this study, nanostructured microparticles was developed with polycaprolactone (PCL), poly(vinyl alcohol) (PVAL) and nanoparticles of the commercial sodium clay NT-25®by using the spray drying technique. The systems obtained were characterized by Nuclear Magnetic Resonance (NMR), scanning Electron Microscopy (sEM), Fourier Transform Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Dynamic Laser Light scattering (DLs) and Differential scanning Calorimetry (DsC). The NMR sup>13sup>C and FTIR techniques showed that both polymers were present in the microparticles and the DsC analysis revealed a small variation in the glass transition temperature of the PCL. The XRD and sEM analyses showed that the microparticles produced were amorphous and had a concave morphology. The NT-25 nanoload reduced the microparticles’ size due to the multiple interactions formed in the hybrid nanocomposite material. Therefore, it was possible to develop microparticles by using biodegradable and biocompatible polymers, with different polarities, allowing the incorporation of hydrophilic and hydrophobic materials and enabling the inclusion of otherwise incompatible materials in the same system.

关键词： Microparticles spray Drying Polycaprolactone Poly(Vinyl Alcohol) sodium Clay NT-25

Evaluation of Nevirapine Release Kinetics from Polycaprolactone Hybrids

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Materials sciences and Applications 2016年第11期7卷 680-701页

作者： mariana s. s. b. Monteiro Jackeline Lunz Pedro J. sebastião maria inês b.uno tavares Faculdade de Farmácia Universidade Federal do Rio de Janeiro Centro de Ciências da Saúde Bloco L Cidade Universitária Ilha do Fund&atilde o Rio de Janeiro Brazil Instituto de Macromoléculas Professora Eloísa Mano Universidade Federal do Rio de Janeiro Centro de Tecnologia Bloco J Cidade Universitária Ilha do Fund&atilde o Rio de Janeiro Brazil Departamento de Física Instituto Superior Técnico Technical University of Lisbon Lisbon Portugal

The Nevirapine (NVP)/Polycaprolactone (PCL)/Nanoparticles hybrids systems have been developed as a potential platform for drug delivery, by solvent cast, as thin films. NVP, an antiretroviral drug, was included within PCL matrix containing three types of nanoparticles: an organoclay layered silicate Viscogel s7®(3% w/w), hydrophilic silica oxide particles Aerosil®A20 (0.25% w/w) and titanium dioxide particles (0.25% w/w). These systems were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), low-field nuclear magnetic resonance (NMR), ultraviolet-visible spectroscopy (UV), in-vitro dissolution testing and drug release mechanism kinetics. The PCL crystallization was affected by NVP incorporation, modifying its semi-crystalline structure to a less ordered structure. When nanoparticles and NVP were added, the Tsub>1sub>H values increased, for PCL, PCL/s7, PCL/ siOsub>2sub> and PCL/TiOsub>2sub> hybrids, suggesting that its addition produced a new material, with less molecular mobility, due to the new intermolecular interactions formation. It can consider a structure formation among the PCL chains, nanoparticles and NVP, with strong forces in the PCL/siOsub>2sub>/NVP system. The amount of NVP included was around 1.5 ± 0.03 mg/cmsup>2sup>. In the in-vitro dissolution test, the PCL/siOsub>2sub>/NVP system released the smallest amount of drug and this result could be attributed to the strong intermolecular interaction between the drug and the PCL/siOsub>2sub> system. Higuchi’s model was the mathematical model chosen to treat the release data, since this model presented the highest coefficient correlation (r) value. The drug release probably occur by diffusion through the matrix pores, thus, these materials are suitable for sustained release of NVP.

关键词： Polycaprolactone Nevirapine Hybrids Modified Release

Carbon-13 solid state NMR Techniques to Evaluate the Morphology of PP/TiO<sub>2sub> Composites

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Materials sciences and Applications 2016年第1期7卷 20-25页

作者： Igor Lopes soares maria inês b.uno tavares André Luis b. b. e silva Antonio Gabriel Malagueta Feio Instituto de Macromoléculas Universidade Federal do Rio de Janeiro Rio de Janeiro Brazil Instituto Federal do Mato Grosso IFMT Mato Grosso Brazil CENIMAT/I3N Departamento de Ciência dos Materiais Faculdade de Ciências e Tecnologia Universidade Nova de Lisboa Caparica Portugal

solid state NMR was successfully used to determine the proton spin-lattice relaxation time in the rotating frame (T1ρH) for systems based on polypropylene (PP) and PP with titanium dioxide (TiOsub>2sub>) organically modified or unmodified incorporated, in order to understand the molecular behavior of these systems. These techniques were employed in the samples organically modified and unmodified TiOsub>2sub> to investigate the effect of organic modification on the dispersion and distribution of the particles in the PP matrix. The results were analyzed in terms of the effect of the particles organic modified or not according to the intermolecular interaction in the composites. According to the T1ρH values, all composites showed at least two domains: the short values were related to the rigid part, which included the crystalline and amorphous phase constricted in it, while the longer times were attributed to the amorphous region, which had higher molecular mobility compared to the rigid region of the materials. The increase in the relaxation time parameter in the composites compared to the pure PP was associated to the strong interaction between titanium dioxide particles and the polymer chains. This effect was more pronounced for the systems containing organically modified TiOsub>2sub>. According to the results, it could be inferred that intermolecular interaction occurred in the CHsub>2sub> and CH groups, being more intense with CHsub>2sub> groups. Finally, the solid state NMR techniques were able to evaluate the molecular dynamics of those systems.

关键词： NMR PP TiO2 Composites

Quality of Electroless Ni-P (Nickel-Phosphorus) Coatings Applied in Oil Production Equipment with salinity

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials science and Chemical Engineering 2013年第6期1卷 1-8页

作者： Fernando b. Mainier maria P. Cindra Fonseca sérgio s. M. tavares Juan M. Pardal Escola de Engenharia Universidade Federal Fluminense (UFF) Niterói Brazil

The corrosion resistance of nickel-phosphorus (Ni-P) coatings and their mechanical properties in seawater have led inestigations into the development of new technologies and the replacement of some special alloys in equipment used in oil production, such as valves, tubing, sucker rod joints, pumps, riser, manifolds and subsea Christmas trees. These studies began with brenner and Riddel who developed, in the 1940s, formulations for Ni-P deposition on carbon steel without using an electric current. Joint deposition of nickel and phosphorus on a metallic surface (carbon steel) without applying an external current is accomplished using cathodic reduction with hydrogen (H) from a reducing agent (sodium hypophosphite) and nickel salts. To assure good performance of a Ni-P coating, the deposit quality must be inspected and evaluated during the chemical deposition process or in the end product. The recommended test parameters are: thickness, layer uniformity, hardness, adhesion, porosity, corrosion resistance and chemical composition of the nickel-phosphorus coating. The purpose of this paper was to investigate the Ni-P coating process, to evaluate the b?haviour of Ni-P in a saline environment using aqueous brine (3.5% - 30% sodium chloride by mass) and to present possible defects that could compromise the coating.

关键词： Nickel-Phosphorus (Ni-P) Coatings Corrosion Petroleum Test

The Use of solid state NMR to Evaluate the Carbohydrates in Commercial Coffee Granules

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Food and Nutrition sciences 2011年第4期2卷 350-355页

作者： Regina Freitas Nogueira Elisangela Fabiana boffo maria inês b.uno tavares Leonardo AMoreira Leila Aley tavares Antonio Gilberto Ferreira Departamento de Química da Universidade Federal de Sao CarlosSao CarlosBrasil Institutito de Macromoléculas Universidade Federal do Rio de JaneiroRio de JaneiroBrasil Escola Técnica Federal de Minas GeraisBrasil

Coffee brings many health benefits due to its chemical constituents. based on this information, it is essential to know the main chemical compounds from coffee granules;the intermolecular interaction among the coffees compounds and the molecular components homogeneity. In this study six types of roasted commercial coffee were evaluated by solid state nuclear magnetic resonance (NMR), employing carbon-13 (13C) and hydrogen (1H) nucleus. Carbon-13 was analyzed applying high field NMR techniques, such as: magic angle spinning (MAs);magic angle spinning with cross-polariza- tion (CPMAs) and magic angle spinning with cross-polarization and dipolar dephasing (CPMAsDD). The hydrogen was evaluated via relaxation times. Proton spin-lattice relaxation time in the rotating frame was deter-mined through the carbon-13 decay, during the variable contact-time experiment, using high field NMR. Proton spin-lattice relaxation time was determined through the inversion-recovery pulse sequence, using low field NMR. Considering all NMR results, it was concluded that the major coffee compounds are: a) triacilglycerides, which constitute the mobile region in the granule coffee and b) Carbohydrates such as: polysaccharides and fibers that belong to the rigid domain. These constituents belong to different molecular mobility domain, although they have strong intermolecular interactions due to the granule organization.

关键词： solid state NMR Coffee

Gold supported on Metal Oxides for Carbon Monoxide Oxidation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2011年第2期4卷 180-193页

作者： sonia A. C. Carabineiro Nina bogdanchikova Miguel Avalos-borja Alexey Pestryakov Pedro b. tavares Jose L. Figueiredo Laboratário de Catálise e Materiais Associate Laboratory LSRE/LCM Departamento de Engenharia Química Faculdade de Engenharia Universidade do Porto 4200-465 Porto Portugal Universidad Nacional Autónoma de México Centro de Nanociencias y Nanotecnologia Carretera Tijuana-Ensenada 22800 Ensenada Baja California México Tomsk Polytechnic University 30 Lenin Avenue Tomsk 634050 Russia Universidade de Trás-os-Montes e Alto Douro Centro de Quimica-Vila Real Departamento de Química 5001-911 Vila Real Portugal

Au has been loaded （1% wt.） on different commercial oxide supports （CuO, La2O3, Y2O3, NiO） by three different methods： double impregnation （DIM）, liquid-phase reductive deposition （LPRD）, and ultrasonication （Us）. samples were characterised by N2 adsorption at -196℃, high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectrometry, high-angle annular dark-field imaging （Z-contrast）, X-ray diffraction, and temperature programmed reduction. CO oxidation was used as a test reaction to compare the catalytic activities. The best results were obtained with Au loaded by DIM on the NiO support, with an activity of 7.2 × 10^（-4） molco·gAu^（-1）·s^（-1） at room temperature. This is most likely related to the Au nanoparticle size being the smallest in this catalyst （average 4.8 nm）, since it is well known that gold particle size determines the catalytic activity. Other samples, having larger Au particle sizes （in the 2-12 nm range, with average sizes ranging from 4.8 to 6.8 nm）, showed lower activities. Nevertheless, all samples prepared by DIM had activities （from 1.1 × 10^（-4） to 7.2 × 10^（-4） molco·gAu^（-1）·s^（-1）, at room temperature） above those reported in the literature for gold on similar oxide supports. Therefore, this method gives better results than the most usual methods of deposition-precipitation or co-precipitation.

关键词： Gold heterogeneous catalysis oxidation electron diffraction X-ray diffraction