On the development of the electrochemical potentiokinetic method

The development of electrochemical potentiokinetic methods as applied to the testing of metals and alloys is followed from its early phases up to its latest advances relating to intergranular corrosion, SCC and pitting corrosion tests of stainless steels and special alloys and to the examination of their structure and properties. In assessing the susceptibility to intergranular and pitting corrosion by potentiokinetic polarization tests, the polarization curves which apply to the bulk of the alloy grains (the matrix) must be distinguished from those pertaining to grain boundaries. Cyclic polarization measurements such as the electrochemical potentiokinetic reactivation (EPR) test make it possible to derive the alloy's susceptibility to intergranular, pitting and crevice corrosion from characteristic potentials and other quantities determined in the 'double loop' test. EPR is rapid and responds to the combined effects of a number of factors that influence the properties of materials. The electrochemical p otentiokinetic tests are sensitive enough to detect structural changes in heat treated materials ranging far beyond the stainless steels alone, and can be used for non-destructive testing aimed at elucidating the properties and behavior of materials. © 2001 Elsevier Science Ltd. All rights reserved.

Phase transformations in the Cu-Al alloy with Ag addition

The effect of Ag addition on the phase transformations that occur in the Cu-10% Al alloy was studied using differential thermal analysis, scanning electron and optical microscopies and energy dispersive X-ray analysis. The results indicated that Ag addition is responsible for the separation of the reverse martensitic transformation in two stages, and for the refinement of the α-phase grains. The relative amount of the β1 martensitic phase, retained on slow cooling (above 2 K min-1 of cooling rate), and the relative fraction of phase α2 are increased. The solubility limit of Ag in the matrix is close to 6 mass% and at this concentration the maximum stability of the β-phase is reached. © 2005 Akadémiai Kiadó, Budapest.

Optimization of a novel nitric oxide sensor using a latex rubber matrix

This study present a novel NO sensor made of a spin trap (iron(II)-diethyldithiocarbamate complex, FeDETC) incorporated in a latex rubber matrix and works as a trap for NO, which is detectable by Electron Paramagnetic Resonance (EPR). We explored the optimization of our sensors changing systematically two fabrication parameters: the latex rubber matrix temperature of polymerization and FeDETC concentration inside the matrix. The sensor was prepared in four different temperatures: 4, 10, 20 and 40°C. The FeDETC concentration was also varied from 0.975 to 14.8 mM. We observed a variation of the EPR signals from the sensors prepared at different conditions. We found a high stability of the EPR response from our sensor, 40 days at RT. The best sensor was made with a latex rubber matrix polymerized at 10°C and with a FeDETC concentration of 14.8 mM. In vivo tests show good biocompatibility of our sensor. © 2007 Asian Network for Scientific Information.

Using tree population size structures to assess the impacts of cattle grazing and eucalypts plantations in subtropical South America

To evaluate the effects of distinct management of the matrix in which forest fragments are found upon plant populations thriving in forest remnants in south Brazil, we assessed the conservation status of populations of four woody species (Campomanesia rhombea, Diospyros incontans, Myrciaria cuspidata and Sebastiania commersoniana) through analyses of size structure. Analyzes were carried out at two scales. At a local scale, we consider populations in fragments surrounded by pastures or eucalypts forest plantations, and at a regional scale we also consider larger forest tracts taken as reference areas (Rio Grande do Sul Forest Inventory databank). Population size structures were summarized using the symmetry of height distributions. Small individual size classes prevailed at the local scale in fragments surrounded by eucalypts plantations, whereas in areas exposed to cattle ranching, populations of the same species consistently lack small individuals. At the regional scale, populations in fragments surrounded by pastures presented greater skewness (prevalence of small plants) than populations in reference areas, while populations surrounded by eucalypts plantations presented intermediate skewness. These results reinforce the notion that plantations have a higher conservation value for forest ecosystems than other commercial land uses, like cattle ranching. © 2010 Springer Science+Business Media B.V.

Incorporation of dithiooxamide as a complexing agent into cellulose for the removal and pre-concentration of Cu(II) and Cd(II) ions from natural water samples

The present study describes the incorporation of a complexing agent, dithiooxamide, into microcrystalline cellulose for use in the pre-concentration of Cu(II) and Cd(II) ions from aqueous samples. The FTIR spectrum of the adsorbent exhibited an absorption band in the region of 800 cm-1, which confirmed the binding of the silylating agent to the matrix. Elemental analysis indicated the amount of 0.150 mmol g-1 of the complexing agent. The adsorption data were fit to the modified Langmuir equation, and the maximum amount of metal species extracted from the solution, Ns, was determined to be 0.058 and 0.072 mmol g-1 for Cu(II) and Cd(II), respectively. The covering fraction φ, which was 0.39 and 0.48 for Cu(II) and Cd(II), respectively, was used to estimate a 1:2 (metal:ligand) ratio in the formed complex, and a binding model was proposed based on this information. The adsorbent was applied in the pre-concentration of natural water samples and exhibited an enrichment factor of approximately 50-fold for the species studied, which enabled its use in the analysis of trace metals in aqueous samples. The system was validated by the analysis of certified standard (1643e), and the adsorbent was stable for more than 20 cycles, thus enabling its safe reutilization. © 2012 Elsevier B.V. All rights reserved.

Silver colloidal nanoparticles: Effect on matrix composition and structure of Candida albicans and Candida glabrata biofilms

Aim: The aim of this study was to assess the effect of different silver nanoparticles (SN) concentrations on the matrix composition and structure of Candida albicans and Candida glabrata biofilms. Methods and Results: Candida biofilms were developed in 6-well microtiter plates during 48 h. After, these biofilms were exposed to 13·5 or 54 μg SN ml-1 for 24 h. Then, extracellular matrices were extracted from biofilms and analysed chemically in terms of proteins, carbohydrates and DNA. To investigate the biofilm structure, scanning electron microscopy (SEM) and epifluorescence microscopy were used. SN interfered with the matrix composition of Candida biofilms tested in terms of protein, carbohydrate and DNA, except for the protein content of C. albicans biofilm. By SEM, Candida biofilms treated with SN revealed structural differences, when compared with the control groups. Further, SN showed a trend of agglomeration within the biofilms. Epifluorescence microscopy images suggest that SN induced damage on cell walls of the Candida isolates tested. Conclusions: In general, irrespective of concentration, SN affected the matrix composition and structure of Candida biofilms and these findings may be related to the mechanisms of biocide action of SN. Significance and Impact of the Study: This study reveals new insights about the behaviour of SN when in contact with Candida biofilms. SN may contribute to the development of therapies to prevent or control Candida infections. © 2012 The Society for Applied Microbiology.

Synthesis of PTSH-modified CeO2 nanoparticles: Effect of the modifier on structure, optical properties, and dispersibility

CeO2 nanoparticles were synthesized by the precipitation method and modified with para-toluene sulfonic acid (PTSH), either in situ or post-synthesis. The presence of PTSH in the samples was confirmed by FTIR. PXRD and FTIR analyses showed that the post-synthesis PTSH modification altered the CeO2 structure, whereas the in situ modification maintained intact the crystalline structure and UV-vis absorbance properties. For both in situ and post-synthesis modifications, TEM images revealed the presence of nanoparticles that were 5nm in size. The dispersibility of the in situ PTSH-modified material in a hydrophilic ureasil-poly(ethylene oxide) matrix was investigated using SAXS measurements, which indicated that CeO2 nanoparticles modified with PTSH in situ were less aggregated within the matrix, compared to unmodified CeO2 nanoparticles. © 2013 Elsevier B.V.

Zymographic patterns of MMP-2 and MMP-9 in the CSF and cerebellum of dogs with subacute distemper leukoencephalitis

Distemper leukoencephalitis is a disease caused by the canine distemper virus (CDV) infection. It is a demyelinating disease affecting mainly the white matter of the cerebellum and areas adjacent to the fourth ventricle; the enzymes of the matrix metalloproteinases (MMPs) group, especially MMP-2 and MMP-9 have a key role in the myelin basic protein fragmentation and in demyelination, as well as in leukocyte traffic into the nervous milieu. To evaluate the involvement of MMPs during subacute distemper leukoencephalitis, we measured the levels of MMP-2 and MMP-9 by zymography in the cerebrospinal fluid (CSF) and in the cerebellum of 14 dogs naturally infected with CDV and 10 uninfected dogs. The infected dogs presented high levels of pro-MMP-2 in the CSF and elevated levels of pro-MMP-2 and pro-MMP-9 in the cerebellar tissue. Active MMP-2 was detected in the CSF of some infected dogs. As active MMP-2 and MMP-9 are required for cellular migration across the blood-brain barrier and any interference between MMPs and their inhibitors may result in an amplification of demyelination, this study gives additional support to the involvement of MMPs during subacute distemper leukoencephalitis and suggests that MMP-2 and MMP-9 may take part in the brain inflammatory changes of this disease. © 2013 Elsevier B.V.

Matrix Effects on Water Analysis for Alkylphenols Using Solid Phase Extraction Gas Chromatography-Mass Spectrometry

Gas chromatography with mass spectrometry is frequently used for the quantification of many classes of substances, including alkylphenols. Alkylphenol polyethoxylates are nonionic surfactants used in a wide variety of industrial and consumer applications. Alkylphenol polyethoxylates can degrade to alkylphenols, which are endocrine disruptors. In analytical validation procedures, the most common parameters studied are the detection and quantification limits, linearity, and recovery; however, the matrix effects are sometimes neglected. Although some investigators have evaluated matrix effects, there is no consensus on how to evaluate them during method validation. In this study, the matrix effects of alkylphenol polyethoxylates (nonylphenol monoethoxylate, nonylphenol diethoxylate, octylphenol monoethoxylate, octylphenol diethoxylate) and alkylphenols (nonylphenol and octylphenol) were studied using solid phase extraction and gas chromatography-mass spectrometry analysis. For alkylphenol polyethoxylates, the matrix effects ranged from 16 to 4692%, whereas for alkylphenols (nonylphenol and octylphenol), the effects were insignificant. Therefore, constructing an analytical curve in the matrix for alkylphenol polyethoxylates is essential. © 2013 Copyright Taylor and Francis Group, LLC.

Effect of colloidal silica on the mechanical properties of fiber-cement reinforced with cellulosic fibers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Measurement of the rotational inertia of bodies by using mechanical spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development of hydrophilic nanocarriers for the charged form of the local anesthetic articaine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of alpha-nickel (II) hydroxide particles on organic-inorganic matrix and its application in a sensitive electrochemical sensor for vitamin D determination

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The Th17 pathway in the peripheral lung microenvironment interacts with expression of collagen V in the late state of experimental pulmonary fibrosis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Bainitic precipitation in the Cu-9 wt.%Al-4 wt.%Mn-5 wt.%Ag alloy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)