A mathematical model for repetitive behaviors of Covid-19

Covid-19 pandemic waves have been hitting us again and again in the past couple years in many countries, while the reason why they come in such repetitive manners remains unexplained, which have brought us with lingering anxieties and economic stagnations. We proposed a mathematical model to describe the mechanism of the repetitive appearance of the number of new cases based upon the SIQR model in which Q (quarantined infectors) were distinguished from I (un-quarantined ones). The repetitive behavior of the pandemic was simulated by an activator-inhibitor system around a fixed point in a phase space as a kind of self-organized oscillations. Periods between each wave were confirmed to be approximately similar. Repetitive behaviors were also observed in actual Covid-19 data. Practical policies and actions were discussed on the ways to effectively control the repetition of pandemic, and proactive PCR test especially after the peak-out stage is highly recommended.

Research progress of microcapsule self-healing anticorrosive coatings

During the long-term use of the coating, environmental factors, physical damage or other factors may cause micro-cracks in the coating. The expansion of microcracks will destroy the overall structure of the coating, reduce the protective effect of the coating and degrade its mechanical properties. However, the traditional repair methods need to consume a lot of manpower and material resources, and the micro-cracks in the coating are difficult to be repaired by the traditional external means. Inspired by biological systems, intelligent coatings with certain self-healing ability have attracted wide attention in academia and industry. According to the different remediation agents used in self-healing micro capsules, several common self-healing coating systems of micro capsules were analyzed, including corrosion inhibitor system, capsule drying oil system, capsule reactive repair agent system, etc.

Multifunctional Inhibitor Mixture for Reducing Bacteria Growth and Corrosion on Marine Grade Steel

<p><a></a>High strength steel in marine environments suffers from severe corrosion susceptibility and the presence of bacteria can exacerbate the effect, accelerating degradation via microbiologically influenced corrosion (MIC). Here we propose a novel approach to MIC inhibition by designing a system capable of limiting the effects of both bacteria growth and corrosion. The combination of a newly synthesised compound, cetrimonium 4-hydroxycinnamate, with lanthanum 4-hydroxycinnamate was the only system tested to date that could both inhibit abiotic corrosion in artificial seawater and minimise bacteria consortium densities over an exposure period of 24 hours. </p> <p>The electrochemical data for the La+Cet mixture demonstrated the significant inhibition of both abiotic corrosion to a level similar to La(4OHCin)₃, as well as the ability to reduce bacteria densities of single strains and a consortium. This is unlike the La+CetNal mixture which accelerated abiotic corrosion and the La+IMI which had an insignificant effect on microbial densities (Catubig et al. 2020). </p> <p>A compatible mixture of ionic inhibitors was achieved by using the same cinnamate anion. </p> <p>This mixture of Cet-4OHCin and La(4OHCin)₃ demonstrated significant abiotic corrosion inhibition and bacteria density reductions, making it a strong candidate as an MIC inhibitor system for 80HLES. </p> <p>The Cet-4OHCin compound and its mixture with La(4OHCin)₃ retained relatively low sensitivity towards skin and intestinal cells, making it a safer and more attractive alternative than other more hazardous corrosion inhibitor materials. </p>

Multifunctional Inhibitor Mixture for Reducing Bacteria Growth and Corrosion on Marine Grade Steel

<p><a></a>High strength steel in marine environments suffers from severe corrosion susceptibility and the presence of bacteria can exacerbate the effect, accelerating degradation via microbiologically influenced corrosion (MIC). Here we propose a novel approach to MIC inhibition by designing a system capable of limiting the effects of both bacteria growth and corrosion. The combination of a newly synthesised compound, cetrimonium 4-hydroxycinnamate, with lanthanum 4-hydroxycinnamate was the only system tested to date that could both inhibit abiotic corrosion in artificial seawater and minimise bacteria consortium densities over an exposure period of 24 hours. </p> <p>The electrochemical data for the La+Cet mixture demonstrated the significant inhibition of both abiotic corrosion to a level similar to La(4OHCin)₃, as well as the ability to reduce bacteria densities of single strains and a consortium. This is unlike the La+CetNal mixture which accelerated abiotic corrosion and the La+IMI which had an insignificant effect on microbial densities (Catubig et al. 2020). </p> <p>A compatible mixture of ionic inhibitors was achieved by using the same cinnamate anion. </p> <p>This mixture of Cet-4OHCin and La(4OHCin)₃ demonstrated significant abiotic corrosion inhibition and bacteria density reductions, making it a strong candidate as an MIC inhibitor system for 80HLES. </p> <p>The Cet-4OHCin compound and its mixture with La(4OHCin)₃ retained relatively low sensitivity towards skin and intestinal cells, making it a safer and more attractive alternative than other more hazardous corrosion inhibitor materials. </p>

Inhibition of corrosion of mild steel in well water by an aqueous extract of soapnut (Sapindus Trifoliatus)

Inhibition efficiency of an aqueous extract of soapnut (Sapindus Trifoliatus) and Zn2+in controlling corrosion of mild steel in well water at room temperature has been evaluated by using weight loss method, polarization study and AC impedance spectra. Dynamic light scattering and Vickers hardness have also been employed. Weight loss method reveals that the formulation consisting of 10 ml soapnut extract and 50 ppm Zn2+ has 97 % inhibition efficiency in controlling corrosion of mild steel immersed in well water. Synergism parameters suggest that a synergistic effect exists between soapnut extract and Zn2+. Adsorption isotherm of metal surface obeys Langmuir adsorption isotherm. Polarization study reveals that the inhibitor system functions as anodic type of inhibitor. AC impedance spectra confirm the protective film formed on the metal surface. Dynamic light scattering (DLS) study reveals surface is in nano meter scale. The Vickers hardness of metal surface was increases in inhibitor system.

Pattern Dynamics in a Diffusive Gierer–Meinhardt Model

The purpose of the present paper is to investigate the pattern formation and secondary instabilities, including Eckhaus instability and zigzag instability, of an activator–inhibitor system, known as the Gierer–Meinhardt model. Conditions on the Hopf bifurcation and the Turing instability are obtained through linear stability analysis at the unique positive equilibrium. Then, the method of weakly nonlinear analysis is used to derive the amplitude equations. Especially, by adding a small disturbance to the Turing instability critical wave number, the spatiotemporal Newell–Whitehead–Segel equation of the stripe pattern is established. It is found that Eckhaus instability and zigzag instability may occur under certain conditions. Finally, Turing and non-Turing patterns are obtained via numerical simulations, including spotted patterns, mixed patterns, Eckhaus patterns, spatiotemporal chaos, nonconstant steady state solutions, spatially homogeneous periodic solutions and spatially inhomogeneous solutions in two-dimensional or one-dimensional space. Theoretical analysis and numerical results are in good agreement for this diffusive Gierer–Meinhardt model.

Corrosion Protection of Mild Steel by a New Phosphonated Pyridines Inhibitor System in HCl Solution

The adsorption behavior and inhibition mechanism of (1, 4, 7-Tris [hydrogen (6-methylpyridin-2-yl) phosphonate] -1, 4, 7-triazacyclononane) (TPP) on the corrosion of mild steel in 1 M HCl were investigated by weight loss technique, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods for different concentrations at 25°C. The results show that the inhibition efficiency values depend on the amount of immersion times and the concentration. A 90% efficiency is found at the highest concentration of the studied compound according to weight loss measurements. The adsorption of the investigated inhibitor on the mild steel surface was well supported using an AFM study. For the assignment of the absorption sites, we performed quantum chemical calculations with (DFT) method. The interaction between the inhibitor and iron surface were performed by molecular dynamic (MD) simulations. In this paper, experimental methods and results used to assess the efficiency of the studied compound are presented.

Corrosion Inhibition Performance of Mild Steelusing L-Tryptophan with Sodium Potassium Tartrate in 0.1 M HCL

The corrosion inhibition characteristics of nitrogen containing amino acid tryptophan (250ppm)with 0.05g of SPTon mild steel in0.1M HCl, was studied by various techniques. Weight loss method analysis showed that there is an increase in inhibition efficiency by increasing the concentration of inhibitor. Polarization and impedance studies indicated that the present inhibitor system as acathodic type inhibitor. EDAX spectra confirm the presence of inhibiting elements on the metal surface and SEM analysis indicated the smoothness of the layer formed on the surface of the metal.