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Monitoring Cathodic Shielding and Corrosion under Disbonded Coatings
( F. Varela ),( M. Yj Tan ),( B. Hinton ),( M. Forsyth ) 한국부식방식학회 2017 Corrosion Science and Technology Vol.16 No.3
Monitoring of corrosion is in most cases based on simulation of environmental conditions on a large and complex structure such as a buried pipeline using a small probe, and the measurement of thermodynamics and kinetics of corrosion processes occurring on the probe surface. This paper presents a hybrid corrosion monitoring probe designed for simulating deteriorating conditions wrought by disbonded coatings and for measuring current densities and distribution of such densities on a simulated pipeline surface. The concept of the probe was experimentally evaluated using immersion tests under cathodic protection (CP) in high resistivity aqueous solution. Underneath the disbonded area, anodic currents and cathodic currents were carefully measured. Anodic current densities were used to calculate metal loss according to Faraday`s law. Calculated corrosion patterns were compared with corrosion damage observed at the surface of the probe after a series of stringent tests. The capability of the probe to measure anodic current densities under CP, without requiring interruption, was demonstrated in high resistivity aqueous solution. The pattern of calculated metal loss correlated well with corrosion products distribution observed at the array surface. Working principles of the probe are explained in terms of electrochemistry.
Molecular Cloning and Characterization of Mannitol-1-Phosphate Dehydrogenase from Vibrio cholerae
( Rambhatla ),( Prashanthi ),( Sanath Kumar ),( Jared T. Floyd ),( Manuel F. Varela ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.9
Vibrio cholerae utilizes mannitol through an operon of the phosphoenolpyruvate-dependent phosphotransferase (PTS) type. A gene, mtlD, encoding mannitol-1-phosphate dehydrogenase was identified within the 3.9 kb mannitol operon of V. cholerae. The mtlD gene was cloned from V. cholerae O395, and the recombinant enzyme was functionally expressed in E. coli as a 6×His-tagged protein and purified to homogeneity. The recombinant protein is a monomer with a molecular mass of 42.35 kDa. The purified recombinant MtlD reduced fructose 6-phosphate (F6P) using NADH as a cofactor with a Km of 1.54 ± 0.1 mM and Vmax of 320.8 ± 7.81 ?mol/min/mg protein. The pH and temperature optima for F6P reduction were determined to be 7.5 and 37oC, respectively. Using quantitative real-time PCR analysis, mtlD was found to be constitutively expressed in V. cholerae, but the expression was up-regulated when grown in the presence of mannitol. The MtlD expression levels were not significantly different between V. cholerae O1 and non-O1 strains.
Monitoring Cathodic Shielding and Corrosion under Disbonded Coatings
Varela, F.,Tan, M. YJ,Hinton, B.,Forsyth, M. The Corrosion Science Society of Korea 2017 Corrosion Science and Technology Vol.16 No.2
Monitoring of corrosion is in most cases based on simulation of environmental conditions on a large and complex structure such as a buried pipeline using a small probe, and the measurement of thermodynamics and kinetics of corrosion processes occurring on the probe surface. This paper presents a hybrid corrosion monitoring probe designed for simulating deteriorating conditions wrought by disbonded coatings and for measuring current densities and distribution of such densities on a simulated pipeline surface. The concept of the probe was experimentally evaluated using immersion tests under cathodic protection (CP) in high resistivity aqueous solution. Underneath the disbonded area, anodic currents and cathodic currents were carefully measured. Anodic current densities were used to calculate metal loss according to Faraday's law. Calculated corrosion patterns were compared with corrosion damage observed at the surface of the probe after a series of stringent tests. The capability of the probe to measure anodic current densities under CP, without requiring interruption, was demonstrated in high resistivity aqueous solution. The pattern of calculated metal loss correlated well with corrosion products distribution observed at the array surface. Working principles of the probe are explained in terms of electrochemistry.
An Overview of New Progresses in Understanding Pipeline Corrosion
( M. Yj Tan ),( F. Varela ),( Y. Huo ),( R. Gupta ),( D. Abreu ),( F. Mahdavi ),( B. Hinton ),( M. Forsyth ) 한국부식방식학회(구 한국부식학회) 2016 Corrosion Science and Technology Vol.15 No.6
An approach to achieving the ambitious goal of cost effectively extending the safe operation life of energy pipeline to 100 years is the application of health monitoring and life prediction tools that are able to provide both long-term remnant pipeline life prediction and in-situ pipeline condition monitoring. A critical step is the enhancement of technological capabilities that are required for understanding and quantifying the effects of key factors influencing buried steel pipeline corrosion and environmentally assisted materials degradation, and the development of condition monitoring technologies that are able to provide in-situ monitoring and site-specific warning of pipeline damage. This paper provides an overview of our current research aimed at developing new sensors and electrochemical cells for monitoring, categorising and quantifying the level and nature of external pipeline and coating damages under the combined effects of various inter-related variables and processes such as localised corrosion, coating cracking and disbondment, cathodic shielding, transit loss of cathodic protection.
Room temperature photoluminescence of BCT prepared by Complex Polymerization Method
F.V. Motta,A.P.A. Marques,J.W.M. Espinosa,P.S. Pizani,E. Longo,J.A. Varela 한국물리학회 2010 Current Applied Physics Vol.10 No.1
It was used the Complex Polymerization Method to synthesize barium calcium titanate powders (BCT). Crystalline Ba0.8Ca0.2TiO3 perovskite-type phase could be identified by X-ray diffraction and confirmed by Raman spectroscopy in the powders heat treated at 600 C. Inherent defects, linked to structural disorder,facilitate the photoluminescence emission. The photoluminescent emission peak maximum was around of 533 nm (2.33 eV) for the Ba0.8Ca0.2TiO3. The photoluminescence process and the band emission energy photon showed dependence of both the structural order–disorder and the thermal treatment history. The results revealed that Ba0.8Ca0.2TiO3 (BCT20) is a highly promising candidate material for optical applications.