Study of ph effect on AZ31 magnesium alloy corrosion for using in temporary implants

Currently, magnesium alloys are gaining great interest for medical applications due to their degrading properties in the human body ensuring a great biocompatibility. These alloys also provide profitable mechanical properties due similarities with human bone.  However, a difficulty in applying these materials in the biomaterials industries is the corrosion prior to cell healing. The effect of the chemical composition of Mg alloys on their corrosion behavior is well known. In this study, samples of AZ31 magnesium alloy were cut into chips for elemental chemical analysis by neutron activation analysis (NAA). Concentrations of the elements As, La, Mg, Mn, Na, Sb and Zn were determined in the AZ31 alloy. Visualization tests of agar corrosion development in various media, of 0.90% sodium chloride solution (mass), phosphate buffer saline (PBS) and simulated body fluid (SBF) were performed. Visualizations of the effect of agar gel corrosion revealed pH variation during the corrosion process due to the released into the cathode. The highest released of hydroxyl ions occurred in NaCl solution compared to PBS and SBF solutions indicating that NaCl solution was much more aggressive to the alloy compared to the others

A study on corrosion resistance of ISO 5832-1 austenitic stainless steel used as orthopedic implant

The ISO 5832-1 austenitic stainless steel used as biomaterial is largely applied in the area of orthopedics, especially in the manufacture of implants, such as temporary or permanent replacement of bone structures. The objective of this study was to evaluate the localized corrosion resistance of the ISO 5832-1 stainless steel used in orthopedic implants by electrochemical tests in two different solutions. The results of this study are of great interest to evaluate the corrosion of metallic implants that can result in the release of corrosion products into bodily fluids causing possible adverse biological reactions. The determination of the chemical elements in the composition of the ISO 5832-1 stainless steel was performed by neutron activation analysis (NAA). The samples for electrochemical tests were grinded with silicon carbide paper up to #4000 finishing, followed by mechanical polishing with diamond paste. The open circuit potential measurements and anodic polarization curves were obtained in solution of 0.90 wt. % of NaCl and of simulated body fluid (SBF). The results indicated that the ISO 5832-1 stainless steel presented a high resistance to crevice corrosion in simulated body fluid solution but high susceptibility to this form of corrosion in the chloride solution. &nbsp

The Application of Bio-Emulsion from Soybean Oil Partially Epoxidized as a Maintenance Technique for Flexible Pavements

An increase in the use of biomaterials has been noted in recent years because of several impacts caused by human activities, especially for engineering and paving industry benefits. Several renewable resources, such as a nonfood source of soybean oil, have been successfully tested on modification of asphalt binders. However, their impact on the pavement life cycle is still unknown. Thereby, the objective of this research was to investigate soybean oil as a new, green supply for the maintenance of flexible pavements. The experimental plan consisted of the construction of field test sections through the application of sub-epoxidized soybean oil (SESO) over a flexible pavement surface. Rates of 0.1 and 0.3 L/m2 were chosen, and the main tests intended for study were functional procedures including the British pendulum and sand patch tests on the pavement surface, which were complemented with the indirect tensile strength test for mechanical analysis. The change in the chemical composition of the recovered binder was analyzed by thin layer chromatography and Fourier-transform infrared spectroscopy. The rheological properties were analyzed by frequency sweep, linear amplitude sweep, and multiple stress creep and recovery, and the tests were carried out with a dynamic shear rheometer. The effects of the SESO bio-emulsion demonstrated a rejuvenating activity on the properties of the aged binder, with mechanical and rheological improvements for both analyzed rates. A further investigation is indicated to evaluate the influence of time on the modification studied in this work. Such testing could ensure the use of SESO bio-emulsion as an environmentally friendly alternative for the maintenance of flexible pavements.This article is published as A. P. da Silva, C. C. Falcão, A. F. J. Uchôa, S. H. A. Barroso, R. C. Williams, and M. S. Brito, “The Application of Bio-Emulsion from Soybean Oil Partially Epoxidized as a Maintenance Technique for Flexible Pavements,” Journal of Testing and Evaluation 51, no. 4 (July/August 2023): 2260–2273. https://doi.org/10.1520/JTE20220286. Copyright © 2023 by ASTM International. Posted with permission

PHYTOPLANKTON BIOMASS INCREASES IN A SILT-IMPACTED AREA IN AN AMAZONIAN FLOOD-PLAIN LAKE OVER 15 YEARS

Funding Information: We thank Mineração Rio do Norte S.A. and Limnologia/UFRJ for fieldwork support, Dr. Janet W. Reid (JWR Associates) for language revision, and Leonardo Preza Rodrigues for map charting. VLMH, JCN, FAE, RLB, and FR are partially supported by the National Council for Scientific and Technological Development (CNPq), Brazil, RLB, and FAE by FAPERJ, Brazil, and CGR financially supported by Sakari Alhopuro Foundation, Finland. Publisher Copyright: © 2022, Universidade Federal do Rio de Janeiro. All rights reserved.Tailings from bauxite mining in Porto Trombetas (Pará state, Central Amazonia, Brazil) was discharged (1979–1989) into Batata Lake affecting about 30% of its area. The lake belongs to a clear-water flood-plain system along the Trombetas River, a tributary of the Amazon River. Siltation is the main perceived factor impacting aquatic and flooded communities. Besides natural regeneration, a program to restore a section of igapó forest in the impacted area (IA) has been conducted since 1991. Decreased light is the main factor reducing total phytoplankton biomass (PhyBM) in IA. We hypothesized that PhyBM in IA increases over time because of the improvement of the underwater light conditions due to the natural regeneration and restoration. We sampled quarterly PhyBM and limnological variables (depth, transparency, temperature, pH, conductivity, dissolved oxygen, turbidity, suspended solids, total Kjeldahl nitrogen, and total phosphorus), over 15 years (2005–2019) at eight sampling sites in the two areas (N = 349). We also obtained daily climatic and hydrologic data. PhyBM was higher in NIA than in IA. The temporal trend in the annual mean of PhyBM increased significantly over time only in the IA, approximating the NIA values, confirming our general hypothesis. The increase of PhyBM in the IA was negatively related to the residual light attenuation caused by non-phytoplankton turbidity and to total phosphorus, and positively to air temperature and site depth (p < 0.05; Marginal r2 = 0.18; Conditional r2 = 0.29). Instead, in NIA, PhyBM was explained only by the increase in air temperature (p < 0.05; Marginal r2 = 0.15; Conditional r2 = 0.34). We concluded that the PhyBM in the IA positively responds to the synergy between increasing light availability, air temperature, and site depth, and decreasing total phosphorus concentrations, regardless of hydrologic phase.Peer reviewe