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The virulence and resistance of pathogenic microorganisms are promoted by quorum-sensing (QS) mediated traits and biofilms. The development of antimicrobial agents which can reduce the incidence of microbial resistance by disrupting the establishment of biofilms and QS, constitute a suitable strategy to reduce the emergence of pathogenic strains that are resistant to antibiotics. In this study, 3-(1,3-dithian-2-ylidene) pentane-2,4-dione (1) and ethyl-2-cyano-2-(1,3-dithian-2-ylidene) acetate (2) were successfully synthesized and characterized using EIMS, 1H NMR and 13C NMR techniques. On S. aureus, both compounds had MIC (minimal inhibitory concentrations) of 0.625 mg/mL while on E. coli and C. albicans, compound 2 showed higher activity than compound 1. All compounds inhibited formation of biofilms by C. albicans and S. aureus at sub-MIC with compound 1 being more active than compound 2. On E. coli, only compound 1 inhibited biofilm formation. Violacein production of violacein in C. violaceum CV12472 and quorum sensing in C. violaceum CV026 were inhibited indicating that the compounds could block signal production and reception. Anti-quorum sensing at sub-MIC concentrations revealed by inhibition zones were 13.0±0.5 mm and 8.0±0.5 mm at MIC and MIC/2 respectively for compound 1 and for compound 2, they were 11.5±0.4 mm and 7.5±0.0 mm at MIC and MIC/2 respectively. Concentration-dependent swarming motility was exhibited by both compounds with compound 1 slightly more active than compound 2. The results indicate that the organosulphur compounds could be suitable candidates for modern antibiotics.

Abstract. A novel Butanolic extract of Ephedra major (denoted EBEM) was investigated as corrosion inhibitor for mild steel in 1 M hydrochloric acid solution. The investigation was carried out using weight loss, electrochemical impedance spectroscopy (EIS), Tafel polarization measurements, Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) methods. The effect of temperature on the corrosion behavior of steel in HCl with the addition of the inhibitor was investigated in the temperature range 20-60°C. The inhibition efficiency was observed to increase with increasing concentration of the extract EBEM and deceased with increasing the temperature. Tafel curves have revealed that the EBEM possesses the indices of a mixed inhibitor. The adsorption of the inhibitor on the steel surface, follow Langmuir isotherm and its mode was found to be physical adsorption. Thermodynamic parameter (ΔG°ads) and activation parameters (Ea, ΔHa and ΔSa) were calculated to investigate the mechanism of inhibition. Obtained data were analyzed by suggesting two mathematical models based on linear and quadratic regressions, which takes into account the effect of concentration and temperature upon the inhibition efficiency. Experimental data were in good agreement with those predicted by both models.   Resumen. Se investigó un nuevo extracto butanólico de Ephedra major (denominado EBEM) como inhibidor de la corrosión del acero al carbono en una solución de ácido clorhídrico HCl 1 M. La investigación se llevó a cabo mediante métodos de pérdida de peso, espectroscopia de impedancia electroquímica (EIS), mediciones de polarización de Tafel, espectroscopia infrarroja por transformación de Fourier (FT-IR) y microscopía electrónica de barrido (SEM). Se investigó el efecto de la temperatura en el comportamiento de la corrosión del acero en HCl con la adición del inhibidor en el rango de temperaturas de 20-60°C. Se observó que la eficacia de la inhibición aumentó con el incremento de la concentración del extracto EBEM y disminuye con el aumento de la temperatura. Las curvas de Tafel han revelado que el EBEM posee los índices de un inhibidor mixto. La adsorción del inhibidor en la superficie del acero sigue la isoterma de Langmuir y su modo se encontró que era de adsorción física. Se calcularon los parámetros termodinámicos (ΔG°ads) y de activación (Ea, ΔHa y ΔSa) para investigar el mecanismo de inhibición. Los datos obtenidos se analizaron proponiendo dos modelos matemáticos basados en regresiones lineales y cuadráticas, que tienen en cuenta el efecto de la concentración y la temperatura sobre la eficacia de la inhibición. Los datos experimentales coincidieron con los predichos por ambos modelos.

In this paper, synthesized organic compound of the family of ketene dithioacetal was studied as corrosion inhibitors for mild steel in 1.0 M hydrochloric acid by gravimetric measurement. The aim of this work is to study the effect of inhibitor concentration and the temperature on the resistance, corrosion and to compare the experimental results with mathematical models. The structural properties were performed using scanning electron microscopy technique. It has been found that the inhibition efficiency, increases with increasing inhibitor concentration. The adsorption of studied compounds on mild steel surface follows Langmuir’s isotherm. Obtained data were analyzed by suggesting two mathematical models based on linear and quadratic regression, taking into account the influence of concentration and temperature on the inhibition efficiency. Obtained experimental data were in good agreement with those predicated by the quadratic model

The purpose of this research is to optimize several variables, including fiber length, volumetric fiber percentage, and sodium hydroxide (NaOH) solution concentration, which influence the bending and compression behavior of cementitious composites reinforced with plant-based fibers from Agave americana. Samples of composites based on fibers extracted from Agave americana and a cement matrix were manufactured and prepared according to a reference mortar. Box-Behnken Design (BBD) of Response Surface Methodology (RSM) was employed to build an experimental design to explore their mechanical behavior and to construct a set of mathematical models predictive of their behavior. The first stage of the work includes the extraction and processing of Agave americana fibers and the preparation of cement and Agave americana mortar specimens. The second phase aims to establish mathematical models to forecast the workability of the cement mortar and its strength at 28 days while emphasizing the correlations and interactions between the different components through the Design Expert software.

Ethyl acetate extract of Asphodelus ramosus (ARAE) was examined as an anti-corrosion agent for carbon steel (CS) in 1 M HCl acid medium using different techniques, namely weight loss method, potentiodynamic polarization, and electrochemical impedance spec­troscopy (EIS) at various temperatures and inhibitor concentrations. An inhibition efficiency of 89.81 % was obtained by the weight loss method at the inhibitor concentration of 700 ppm at 293 K. Increasing the temperature decreases the corrosion inhibition rate. Poten­tiodynamic polarization results showed that the extract is adsorbed on CS surface according to the Freundlich isotherm, while negative values of the standard free energy of adsorption (DG0ads) suggested the physical spontaneity of the adsorption reaction. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses were performed to examine the surface morphology of inhibited and uninhibited CS samples. Central composite design (CCD) based optimization was engaged to analyze factors and maximize inhibition efficiency by applying response surface methodology (RSM) using Design-Expert software.

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The title compound, C 9 H 11 NO 2 S 2 , contains a 1,3-dithiane ring which has a twistboat conformation. The dihedral angle between the mean planes of the ethyl acetate group and the dithiane ring is 17.56 (13) . In the crystal, molecules stack in layers up the a-axis direction, however, there are no significant intermolecular interactions present.