1,720,998 research outputs found
Novel magnetodielectric cobalt ferrite-titania-silica ceramic composites with tunable dielectric properties
No full textThe cobalt ferrite (CF)-titania (TiO2)-silica (SiO2) system has been studied to produce new ceramic composites by conventional solid state reaction. The microstructure of the sintered CF-TiO2-SiO2 mixture has been related to compositional modifications in terms of SiO2/TiO2 weight ratio keeping constant the CF weight percentage. Microstructural characterization of the sintered bodies was performed in order to understand microstructure evolution, and to quantify the phases volume fraction. The final compositions after sintering differ significantly from the starting ones as a consequence of the reaction of titania with the ferrite, and the formation of the ilmenite-type CoTiO3. Four different distributed phases are present, depending on the starting SiO2/TiO2 weight ratio. The complex permittivity dispersion of ceramic composites was investigated and correlated to their microstructure. Lastly, CF-SiO2 magneto-dielectric composites are suggested as possible candidates for high frequency applications as miniaturized antennas
Hollow-fiber flow field-flow fractionation and multi-angle light scattering as a new analytical solution for quality control in pharmaceutical nanotechnology
No full textThe rapid development of nanoproducts in pharmaceutical field highlights the need for robust analytical methods to ensure their quality and stability. Nanoparticles of different nature and composition (NPs) are employed for many purposes, such as the improvement of drug solubility/bioavailability and the controlled delivery of drugs. Among NPs features, particle size distribution (PSD) plays a fundamental role in determining NPs properties. Nevertheless the high development of different NPs, authorities such as the FDA and the European Union highlight the lack of robust characterization methods and quality control for nanomaterials.
Among the techniques for the size-characterization of particles, Field-Flow Fractionation (FFF) represents a competitive choice: due to the absence of a stationary phase, the separation mechanism is gentle with total maintenance of the native properties of the analytes. In this paper the microcolumn variant of FFF, the Hollow-Fiber Flow FFF (HF5), is coupled on-line with Multi-Angle Light Scattering (MALS) for the development of methods for the characterization of NPs as quality control in new pharmaceutical field. The HF5-MALS was applied to the size characterization in different preservation conditions of silver polyvinylpyrrolidone-stabilized NPs (AgPVP) used for their antimicrobial activity. The ratio of gyration and hydrodynamic radii of AgPVP was evaluated for fresh and aged NPs, suggesting in this case aggregation rearrangement. The influence of different PVP coating and dilution factor was also studied. Finally the metal ion release was determined in relationship to these shape modifications. The HF5-MALS method is robust and reproducible and it can be considered as an important tool for the development of analytical platform for quality control of NPs
Selective Oxidation of HMF via Catalytic and Photocatalytic Processes Using Metal-Supported Catalysts
No full textIn this study, 5-hydroxymethylfurfural (HMF) oxidation was carried out via both the catalytic and the photocatalytic approach. Special attention was devoted to the preparation of the TiO2-based catalysts, since this oxide has been widely used for catalytic and photocatalytic application in alcohol oxidation reactions. Thus, in the catalytic process, the colloidal heterocoagulation of very stable sols, followed by the spray-freeze-drying (SFD) approach, was successfully applied for the preparation of nanostructured porous TiO2-SiO2 mixed-oxides with high surface areas. The versatility of the process made it possible to encapsulate Pt particles and use this material in the liquid-phase oxidation of HMF. The photocatalytic activity of a commercial titania and a homemade oxide prepared with the microemulsion technique was then compared. The influence of gold, base addition, and oxygen content on product distribution in the photocatalytic process was evaluated
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Shape-Related Toxicity of Titanium Dioxide Nanofibres
Full text linkTitanium dioxide (TiO2) nanofibres are a novel fibrous nanomaterial with increasing applications
in a variety of fields. While the biological effects of TiO2 nanoparticles have been
extensively studied, the toxicological characterization of TiO2 nanofibres is far from being
complete. In this study, we evaluated the toxicity of commercially available anatase TiO2
nanofibres using TiO2 nanoparticles (NP) and crocidolite asbestos as non-fibrous or fibrous
benchmark materials. The evaluated endpoints were cell viability, haemolysis, macrophage
activation, trans-epithelial electrical resistance (an indicator of the epithelial barrier competence),
ROS production and oxidative stress as well as the morphology of exposed cells.
The results showed that TiO2 nanofibres caused a cell-specific, dose-dependent decrease
of cell viability, with larger effects on alveolar epithelial cells than on macrophages. The
observed effects were comparable to those of crocidolite, while TiO2 NP did not decrease
cell viability. TiO2 nanofibres were also found endowed with a marked haemolytic activity, at
levels significantly higher than those observed with TiO2 nanoparticles or crocidolite. Moreover,
TiO2 nanofibres and crocidolite, but not TiO2 nanoparticles, caused a significant
decrease of the trans-epithelial electrical resistance of airway cell monolayers. SEM images
demonstrated that the interaction with nanofibres and crocidolite caused cell shape perturbation
with the longest fibres incompletely or not phagocytosed. The expression of several
pro-inflammatory markers, such as NO production and the induction of Nos2 and Ptgs2,
was significantly increased by TiO2 nanofibres, as well as by TiO2 nanoparticles and crocidolite.
This study indicates that TiO2 nanofibres had significant toxic effects and, for most
endpoints with the exception of pro-inflammatory changes, are more bio-active than TiO2
nanoparticles, showing the relevance of shape in determining the toxicity of nanomaterials.
Given that several toxic effects of TiO2 nanofibres appear comparable to those observed
with crocidolite, the possibility that they exert length dependent toxicity in vivo seems worthy
of further investigation
Characterization of polyethylene and polyurethane microplastics and their adsorption behavior on Cu2+ and Fe3+ in environmental matrices
Full text linkAs the world faces growing environmental challenges, understanding the nature of microplastics—such as Low-Density Polyethylene (LDPE) and Polyurethane (PU)—and their transformation in water-based environments is necessary for predicting and mitigating their effects. In this study, we investigated their physicochemical characteristics, presence of impurities, colloidal behavior, and sorption capacity to understand better how microplastics behave and transform in the environment, including their role in transporting heavy metals. The two types of microparticles investigated fall into distinct size ranges, approximately 70 microns for PE particles and around 5 microns for PU particles. Both samples showed a spherical morphology and an evident surface micro-roughness. The elemental and thermal analysis did not show the presence of any significant metal impurities. The zeta-potential measurements as a function of pH provided insights into the dispersion behavior of microplastics (MPs) in freshwaters, suitable for the growth of Zebrafish (Egg water) and Daphnia magna (Elendt M7 Water). Both materials showed in bidistilled water negative zeta potential (ZP) at natural pH (ZP = − 51.0 ± 4.3 mV at pH = 6.6 and ZP = − 29.5 ± 1.4 mV at pH = 5.6 for LDPE and PU, respectively), justified by the presence of surface-active charged impurities. In saline media, ZP vs. pH curves were flatter, with ZP values near 0 mV, confirming the reduced colloidal stability from higher ionic strength and double-layer compression. Finally, we assessed the metal adsorption capacity to establish the role of microplastics in the transport of heavy metals in the environment. We observed selective adsorption for Cu2+ ions, which was both medium-dependent (more ions adsorbed in Elendt M7) and plastic-dependent, with PU showing a stronger affinity for Cu2+ in MilliQ and Egg water. On the contrary, both plastics showed similar adsorption capacity for Fe3+ ions across all media
NanoTiO2@DNA complex: a novel eco, durable, fire retardant design strategy for cotton textiles
No full textA strategy for the design of cotton flame retardant coatings is described, exploiting the natural intumescent formulation of nucleic acids, the intrinsic thermal inertia of TiO 2 ceramic phase and the strong affinity that TiO 2 nanoparticles shows for amphiphilic biomolecules (e.g. proteins, nucleic acids) and hydrophilic substrates. Two different self-assembled TiO 2 @DNA systems are obtained by mixing two opposite charged TiO 2 nanoparticles suspensions with DNA solution. The colloidal behavior of separate and mixed phases was investigated, as well as the morphological, chemical structure and thermal properties of resulting coatings, in order to make some hypothesis on the observed synergic effects. Scanning electron microscopy (SEM) and Attenuated Total Reflectance (ATR) spectroscopy demonstrated the homogeneous distribution of nano-TiO 2 @DNA based coatings on the treated fabrics. The washing fastness tests evidenced the highly improved performance of hybrid coatings if compared with DNA alone. The flammability and cone calorimetry test results confirmed this positive synergy that resulted quite effective in slowing down (or even blocking) the propagation of a flame within the treated substrates and in improving the resistance of the fabrics to the applied heat flux, these latter leaving increased residues at the end of the test
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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