Electrochemical Noise Analysis of Corrosion Behavior of Stainless Steel 304 Exposed in NaCl and FeCl3 solutions

The authors thanks to the Center of Research and Technological Development in Electrochemistry, S.C. (CIDETEQ) who supported this research with the scholarship conceded by the National Commission on Science and Technology (CONACYT). Also, thanks to the Autonomous University of the Mexican State (UAEM) for the research project conducted in CU UAEM Valle de Mexico (Laboratory of Electrochemical and Corrosion of industrial materials).Electrical parameters such as charge of the event (q), characteristic frequency (fn) and impedance (Zn) obtained from shot-noise theory have been proposed as indicators of the initiation of pitting corrosion, and have played an important role in the construction of corrosion patterns which are a good approximation to examine the evolution of corrosion type in metals and its alloys. Therefore, in this research paper, Electrochemical Noise (EN) signals (potential and current noise data) have been collected from AISI 304 stainless steel exposed to chloride solution to evaluate the pitting corrosion behavior. The electrochemical tests were carried out at standard condition during 24 hours of exposure in two chlorine solutions (NaCl and FeCl ). Noise data analysis was mathematical treated by wavelet transform in order to identify the low frequencies that lead the calculation of q, fn and Zn to plot the corrosion behavior and this was correlated with the Energy Distribution Plots (EDP) and metallographic images. The results of all the time series evaluated reveals a concordance in scale of EDP with the initiation and the growth of pitting.EVALUACIÓN MATEMÁTICA DE ACEROS INDUSTRIALES Y SU COMPORTAMIENTO ELECTROQUÍMICO MEDIANTE INTELIGENCIA ARTIFICIAL Folio asignado 4365/2017/CID Modalidad “D” Investigación Básica Aplicada Área de conocimiento Ingeniería y Tecnología Vigencia 01/06/2017 – 01/06/201

Electrochemical Impedance Spectroscopy (EIS): A Review Study of Basic Aspects of the Corrosion Mechanism Applied to Steels

AC impedance measurements have been applied for over twenty years in electrochemistry and physics to investigate the electrical properties of conductive materials and their interfaces using an external electrical impulse (VOLTAGE, V or CURRENT, I) as driving force. Furthermore, its application has recently appeared to be destined in the Biotechnology field as an effective tool for rapid microbiologic diagnosis of living organism in situ. However, there is no doubt that the electrochemical impedance spectroscopy (EIS) is still one of the most useful techniques around the world for metal corrosion control and its monitoring. Corrosion has long been recognized as one of the most expensive stumbling blocks that concern many industries and government agencies, because it is a steel destructive phenomenon that occurs due to the chemical interaction with aqueous environments and takes place at the interface between metal and electrolyte producing an electrical charge transfer or ion diffusion process. Consequently, it is experimentally possible to determine through the EIS technique the mechanism and control that kinectics of corrosion reactions encounter. First, EIS data is collected through a potentiostat/ galvanostat apparatus. After, it is fitted to a mathematical model (i.e. an equivalent electrical circuit, EEC) for its interpretation and analysis, fundamentally seeking a meaningful physical interpretation. Finally, this review reports some basic aspects of the corrosion mechanism applied to steels through the experimental EIS response using Nyquist or Bode plots. Examples are given for different applied electrochemical impedance cases in which steel is under study intentionally exposed to a corrosive aqueous solution by applying a sinusoidal potential at various test conditions

Low friction coefficient coatings Ni-Cr by magnetron sputtering, DC

Magnetron Sputter Deposition technique with DC was used for the deposition of Ni-Cr coatings on AISI 316 SS like substrate. The cathode with a nominal composition Ni-22 at% Cr was prepared by Mechanical Alloying (MA) technique, with a maximum milling time of 16 hours and, with a high energy SPEX 8000 mill. The coatings were made under Argon atmosphere at room temperature with a power of 100 W at different times of growth. Chemical composition, microstructure, topography, nanohardness and wear of the coatings were evaluated using the techniques of microanalysis by energy dispersive X-ray analyzer (EDAX), X-Ray Diffraction (XRD), atomic Force Microscopy (AFM), Nano-indentation and pin-on-Disk, respectively. After milling, was not detected contamination in the mixtures. XRD analysis revealed that the microstructure of the Ni-Cr alloy was maintained in the coatings with respect to MA powders, with some degree of recrystallization. Nanohardness values were in the order of 8.8 GPa with a Young’s modulus of 195 GPa. The adhesion of the films was evaluated according to their resistance to fracture when these were indented at different loads using Vickers microhardness. The wear test results showed a decrease in the friction coefficient with respect to the increase of thickness’ films, getting a minimum value of 0.08 with a thickness of 1 µm and which correspond with the maximum growing time.Financial support provided by the National Council of Science and Technology (CONACyT), with the number project 135100 from basics science program, and the support offered by CINVESTAV-QRO, México, specially to the Dr. F.J. Espinoza Beltrán

Determinantes perceptuales de la intención de uso de Internet para el desarrollo del capital humano

En el marco de la Teoría del Capital Humano (TCH) y las Tecnologías de Información y Comunicación (TIC) se plantea la relación entre el uso de Internet y las percepciones de utilidad, facilidad y autoeficacia. Los resultados muestran que el determinante principal del uso de Internet es la percepción de utilidad (β = .46). El modelo obtuvo un adecuado ajuste con respecto al modelo de relaciones hipotéticas entre las variables perceptuales y actitudinales sobre la variable intencional. Se discuten las implicaciones del modelo en torno al desarrollo del capital humano y satisfacción del cliente en los ambientes laborales

Tolerance and hyperaccumulation of a mixture heavy metals (Cu, Pb , Hg and Zn) by four aquatic macrophytes

El propósito de este trabajo fue comparar la tolerancia a la exposición de una mezcla de los metales (Cu2+, Pb2+, Hg2+ y Zn2+) así como el nivel de hiperacumulación en Typha latifolia, Lemna minor, Eichhornia crassipes y Myriophyllum acuaticum, para proponer un sistema de bioacumulación selectiva que permita la biorremediación eficiente de cuerpos de agua contaminadosIn the present investigation, four macrophytes, namely Typha latifolia (L.), Lemna minor (L.), Eichhornia crassipes (Mart.) Solms-Laubach, and Myriophyllum aquaticum (Vell.) Verdc, were evaluated for their heavy metal (Cu, Pb, Hg, and Zn) hyperaccumulation potential under laboratory conditions. Tolerance analyses were performed for 7 days of exposure at five different treatments of the metals mixture (CuC2, HgC2, PbC2, and ZnC2). The production of chlorophyll and carotenoids was determined at the end of each treatment. L. minor revealed to be sensitive, because it did not survive in all the tested concentrations after 72 hours of exposure. E. crassipes and M. aquaticum displayed the highest tolerance to the metals mixture. For the most tolerant species of aquatic macrophytes, The removal kinetics of E. crassipes and M. aquaticum was carried out, using the following mixture of metals: Cu (0.5 mg/L) and Hg, Pb, and Zn 0.25 mg/L. The obtained results revealed that E. crassipes can remove 99.80% of Cu, 97.88% of Pb, 99.53% of Hg, and 94.37% of Zn. M. aquaticum withdraws 95.2% of Cu, 94.28% of Pb, 99.19% of Hg, and 91.91% of Zn. The obtained results suggest that these two species of macrophytes could be used for the phytoremediation of this mixture of heavy metals from the polluted water bodies

Scale for assessing the quality of Mexican adults' mealtime habits

To construct a scale for assessing the quality of mealtime habits in a sample of urban Mexican adults, computing the contribution of a set of advisable and unadvisable mealtime habits. Material and Methods. We performed an exploratory factor analysis among 7 472 adults participating in the baseline assessment of the Health Workers Cohort Study, to assess the mealtime habits quality. Likelihood ratio test for difference of two probabilities and test for the difference of two means were used to identify differences between low and high categories of the Mealtime Habits Quality Scale (MHQS) across variables of interest. Results. Participants with the top quality of mealtime habits showed lower rates of overweight, obesity, abdominal obesity, and elevated body fat. They were also more adherent to a prudent dietary pattern than a western dietary pattern, and consumed more fruits and vegetables. Conclusions. Anthropometric and dietary variables differed across MHQS categories. However, further validation of the scale, and assessment of their ability to predict weight gain or related diseases are needed, using prospective and intervention studies

Findings in [99mTc]MAA SPECT/CT in the diagnosis and follow-up of pulmonary embolism after infection by SARS-CoV-2 (COVID-19)

SARS-CoV-2 (COVID-19) infection is a current public health problem that has been shown to cause multiple complications, including pulmonary thromboembolism. The first presented case is a 59-year-old woman with a history of COPD, paroxysmal atrial fibrillation and COVID-19 infection in September 2020, consultation in December 2020 for atypical chest pain with suspected PE, AngioCT of pulmonary vessels was performed negative for emboli, subsequently [99mTc]Tc MAA SPECT/CT was indicated with a report of multiple triangular defects concerning acute pulmonary thromboembolism. A second case is a 70-year-old man with a history of dyslipidaemia, presented COVID-19 infection in September 2020 with a complication of PE with involvement of the left pulmonary artery, followed by [99mTc]Tc MAA SPECT/CT report multiple triangular and not triangles defects concerning pulmonary thromboembolism with signs of reperfusion

Ileal apparent and standardized amino acid digestibility of soybean and colza meal in diets for finishing pigs

Agri-food chains generate by-products such as soybean and colza meal for animal feed. Their nutritional value is variable and should be analysed for better quality control before their inclusion in balanced diets. The objective was to determine the content and ileal apparent and standardized digestibility of protein and amino acids (AA) of soybean (PS) and colza meal (PC) as a source of protein in diets for finishing pigs. The experimental units were arranged in a 3×3 Latin square design repeated. The treatments (T) were T1: PS+corn starch, T2: PC+corn starch, and T3: corn starch (Control), which were randomly assigned to six pigs cannulated in distal ileum (PV 75±1.2 kg). The variables were contents and apparent ileal and standardized ileal digestibility of amino acids in soybean and colza meal. To determine digestibility, chromic oxide was added to the diets. The protein and fat contents were higher in the soybean meal. Ash, crude fibre, neutral detergent fibre, acid detergent fibre, phosphorus and calcium contents were higher in the colza meal. Essential amino acid content was higher in soybean meal, but methionine was higher in colza meal. Apparent ileal digestibility (DIA) of total amino acids was similar (p > 0.05) among protein ingredients; but for lysine and threonine it was higher (p ≤ 0.05) in soybean meal, except methionine. Methionine DIA was 89.78 %, 3.88 % higher (p ≤ 0.05) in colza meal. Standardized ileal digestibility (DIE) of total amino acids was similar (p > 0.05) among ingredients, but lysine and threonine were higher (p ≤ 0.05) in soybean meal. DIE was different (p ≤ 0.05) among ingredients for all amino acids except methionine. Ileal and standardized digestibility of all amino acids were higher in soybean meal, except methionine, which was higher in colza meal. The DIA of total amino acids was similar in both protein ingredients, except lysine and threonine in soybean meal and methionine in colza meal