Improving the Thermal Behavior of Poly(propylene) by Addition of Spherical Silica Nanoparticles

Spherical silica nanoparticles were mixed with a PP matrix and the thermal behavior of the nanocomposites was studied. The nanocomposites presented drastic improvements in the degradation behavior under thermo‐oxidative conditions, showing complex multistep processes. Under inert conditions the improvements were lower. Our results indicate that mechanisms based on the labyrinth effect, nanoconfinement or trapping model, are not able to explain the whole enhanced thermal stability in these nanocomposites. Moreover, the high specific area of the nanoparticles (≈70 m² · g^?1) indicates that processes based on the adsorption of volatile polar products coming from the oxidative degradation mechanism are plausible.

     

Cavitation erosion resistance of deposits processed by plasma transferred arc weldingArticle based on a version presented at the XXXI CONSOLDA,São Paulo,Nov 29–Dec 1 2005.

This work sets out a development of the equipment and an evaluation of the process of powder fed transferred arc plasma welding (PTA powder) with an emphasis on its utilization in coating metallic surfaces out of a flat position. After analysing the possibility of using the process in refurbishing hydraulic turbines eroded by cavitation, an analysis was made of the performance of the process and of the influence of the type of current (constant direct current and pulsed direct current) on resistance to cavitation of Stellite 6 alloy in accordance with ASTM standard G-32/92, by the indirect method. From the Stellite 6 alloy coatings deposited by the PTA process – powder using constant direct current and pulsed direct current, no significant difference was observed in the resistance to cavitation. On the other hand, the resistance to cavitation of the Stellite 6 alloy coatings obtained by the PTA powder process showed a performance higher than that of the Cavitec alloy obtained with the MIG and wire fed PTA welding processes.     

Morphology visualization of irregular shape bacteria by electron holography and tomography

In the current work, irregular morphology of Staphylococcus aureus bacteria has been visualized by phase retrieval employing off‐axis electron holography (EH) and 3D reconstruction electron tomography using high‐angle annular dark field scanning transmission electron microscopy (HAADF‐STEM). Bacteria interacting with gold nanoparticles (AuNP) acquired a shrunken or irregular shape due to air dehydration processing. STEM imaging shows the attachment of AuNP on the surface of cells and suggests an irregular 3D morphology of the specimen. The phase reconstruction demonstrates that off‐axis electron holography can reveal with a single hologram the morphology of the specimen and the distribution of the functionalized AuNPs. In addition, EH reduces significantly the acquisition time and the cumulative radiation damage (in three orders of magnitude) over biological samples in comparison with multiple tilted electron expositions intrinsic to electron tomography, as well as the processing time and the reconstruction artifacts that may arise during tomogram reconstruction.     

Blind source separation for classification and detection of flaws in impact-echo testing

This paper presents a technique for defect detection and material classification based on blind source separation by independent component analysis (ICA) for application in impact-echo testing. The transfer functions between the impact point and the defects in the material are modelled as “sources” for blind source separation. The sensors located on the material surface measure a convolutive mixture of the contribution of each of the defects. From spectral analysis the dominant resonance frequencies, varying from homogeneous to defective material, are selected. These frequencies are processed by instantaneous ICA in order to obtain more information about the defects using bootstrap resampling to analyse the stability of the solution. Results show that source estimates fit well with the theoretical response of the material. In addition, it has been found that the number of defects can be estimated by ICA in simulations and experiments with various defective parallelepiped-shape materials of aluminium alloy series 2000.     

Adsorption of ochratoxin A (OTA) anodic oxidation product on glassy carbon electrodes in highly acidic reaction media: Its thermodynamic and kinetics characterization

We study the thermodynamics and kinetics of the adsorption of a redox couple having quinone nature on glassy carbon electrodes. This couple is produced by the anodic oxidation of mycotoxin ochratoxin A in 10% acetonitrile + 90% 1 M HClO₄ aqueous solution. The quasi-reversible redox couple was studied by both cyclic (CV) and square wave (SWV) voltammetric techniques. The Frumkin adsorption isotherm best described the specific interaction of the redox couple with carbon electrodes. By fitting the experimental data, we obtained values of −28.4 kJ mol⁻¹ and 0.70 ± 0.02 for the Gibbs free energy of adsorption and the interaction parameter, respectively. SWV fully characterized the thermodynamics and kinetics of the adsorbed redox couple, using a combination of the “quasi-reversible maximum” and the “splitting of SW peaks” methods. Average values of 0.609 ± 0.003 V and 0.45 ± 0.06 were obtained for the formal potential and the anodic transfer coefficient, respectively. Moreover, a formal rate constant of 10.7 s⁻¹ was obtained. SWV was also employed to generate calibration curves. The lowest concentration of mycotoxin was 1.24 × 10⁻⁸ M (5 ppb), measured indirectly with a signal to noise ratio of 3:1.     

Transgenic Plants as Low-Cost Platform for Chemotherapeutic Drugs Screening

In this work we explored the possibility of using genetically modified Arabidopsis thaliana plants as a rapid and low-cost screening tool for evaluating human anticancer drugs action and efficacy. Here, four different inhibitors with a validated anticancer effect in humans and distinct mechanism of action were screened in the plant model for their ability to interfere with the cytoskeletal and endomembrane networks. We used plants expressing a green fluorescent protein (GFP) tagged microtubule-protein (TUA6-GFP), and three soluble GFPs differently sorted to reside in the endoplasmic reticulum (GFPKDEL) or to accumulate in the vacuole through a COPII dependent (AleuGFP) or independent (GFPChi) mechanism. Our results demonstrated that drugs tested alone or in combination differentially influenced the monitored cellular processes including cytoskeletal organization and endomembrane trafficking. In conclusion, we demonstrated that A. thaliana plants are sensitive to the action of human chemotherapeutics and can be used for preliminary screening of drugs efficacy. The cost-effective subcellular imaging in plant cell may contribute to better clarify drugs subcellular targets and their anticancer effects.     

Preliminary study on the biodegradation of adipate/phthalate polyester polyurethanes of commercial‐type by Alicycliphilus sp. BQ8

Accumulation of polyurethane (PU) waste has increased considerably due to its extensive use. Even though many efforts are being carried out to develop more biodegradable PU, the use of these new materials is far from being commercially available. Here, we analyzed the susceptibility of solid polyester polyurethanes (PS‐PU) of commercial‐type, to biodegradation by Alicycliphilus sp. BQ8, a polyurethanolytic bacterial strain. Four polyester polyols were synthesized from dipropylene glycol (DPG) or diethylene glycol (DEG), and adipic acid (ADA) or phthalic anhydride (PHA), and were combined with either 4,4′‐ and 4,2′‐methylene diphenyldiisocyanate (MDI) or 2,4‐ and 2,6‐toluene diisocyanate (TDI). Synthesized polyols and PUs were characterized. PU biodegradation was assessed by the capacity of the polymers to support bacterial growth, and by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) spectroscopy, and gas chromatography/mass spectrometry (GC‐MS) analyses. Although all the synthesized PUs supported BQ8 growth, SEM analysis showed that PHA‐based PU foams were the most affected by bacterial growth. FTIR spectroscopy and GC‐MS analyses of bacterial treated PS‐PUs showed that they were attacked at ester and urethane groups, suggesting that esterase and amidase activities are involved. Extra‐cellular and membrane bound esterase activities were detected during the five days of analysis. Our results suggest that solid PHA‐based PUs might be more susceptible than ADA‐based PUs to microbial biodegradation in the environment. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42992.     

Formation and characterization of thin films from phthalocyanine complexes: An electrosynthesis study using the atomic-force microscope

(μ-Cyano)(phthalocyaninato)metal(III) [PcMCN]_n species with a central transition metal ion, such as Fe(III) and Co(III), were used to prepare molecular films on a highly oriented pyrolytic graphite electrode substrate by using the cyclic voltammetry technique. In order to investigate the influence of the ligand on the film properties, 1,8-dihydroxyanthraquinone and 2,6-dihydroxyanthraquinone as bivalent ligands were employed. The structure of the molecular materials was analyzed by infrared spectroscopy. The in situ film formation, texture, composition and conductivity of each film were further investigated using atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and the four-probe technique, respectively. The [PcMCN]_n complexes provided conductive films with an electrical conductivity of 1 × 10^− 6 Ω^− 1 cm^− 1 at 298 K.     

Prevalence of Parkinson's disease in Junín, Buenos Aires Province, Argentina

We investigated the prevalence of Parkinson's disease (PD) in a South American city: Junín, Buenos Aires Province, Argentina. At dwellings systematically selected, the case finding involved household screenings and neurological examinations (i.e., a two-phase survey approach). Only persons 40 years of age or older were eligible (N = 7,765). There were 51 cases of PD identified, yielding a crude prevalence of 656.8 per 100,000 population. The age-specific prevalence was consistently higher in men than women, and it increased with advancing age for both sexes. In addition to prevalence figures. we present tallies related to clinical features of PD, as well as tallies related to other subtypes of parkinsonism.