Comparative study of inhibitory efficacy of methionine and its derivatives in acidic medium by mild steel

Corrosion inhibition effect of L-Methionine (MT1), L-Methionine sulfoxide (MT2) and L-Methionine sulfone (MT3) on mild steel corrosion in 1M HCl solution was studied by using weight loss, electrochemical polarization and electrochemical impedance spectroscopy (EIS) techniques. The experimental results showed that the inhibitory efficiency of the three aminoacids improves with the increase of concentration to reach the maximum value of 95.20% for MT1, 94.14% for MT2 and 88.92% for MT3 for a concentration of 10-3M, which translates that the surface covered by the inhibitor increases with the concentration. The effect of temperature on the corrosion rate was investigated and some thermodynamic parameters were calculated. Polarization studies show that three studied inhibitors suggested that three inhibitors control the anodic as well as cathodic reactions and act as mixed type in nature. The results show that MT1, MT2 and MT3 are good inhibitors, and the adsorption of each inhibitor on mild steel surface obeys Flory-Huggins and Langmuir, with a better fit of the Langmuir isotherm through mixed adsorption (physisorption as well as chemisorption) process. In addition, the quantum approach based on density functional theory (DFT), monte Carlo (MC) and molecular dynamics (MD) simulations was confirmed the reactivity of the studied compound towards the corrosion process

Combined inactivation of the Clostridium cellulolyticum lactate and malate dehydrogenase genes substantially increases ethanol yield from cellulose and switchgrass fermentations

<p>Abstract</p> <p>Background</p> <p>The model bacterium <it>Clostridium cellulolyticum </it>efficiently degrades crystalline cellulose and hemicellulose, using cellulosomes to degrade lignocellulosic biomass. Although it imports and ferments both pentose and hexose sugars to produce a mixture of ethanol, acetate, lactate, H₂and CO₂, the proportion of ethanol is low, which impedes its use in consolidated bioprocessing for biofuels production. Therefore genetic engineering will likely be required to improve the ethanol yield. Plasmid transformation, random mutagenesis and heterologous expression systems have previously been developed for <it>C. cellulolyticum</it>, but targeted mutagenesis has not been reported for this organism, hindering genetic engineering.</p> <p>Results</p> <p>The first targeted gene inactivation system was developed for <it>C. cellulolyticum</it>, based on a mobile group II intron originating from the <it>Lactococcus lactis </it>L1.LtrB intron. This markerless mutagenesis system was used to disrupt both the paralogous <smcaps>L</smcaps>-lactate dehydrogenase (<it>Ccel_2485; ldh</it>) and <smcaps>L</smcaps>-malate dehydrogenase (<it>Ccel_0137; mdh</it>) genes, distinguishing the overlapping substrate specificities of these enzymes. Both mutations were then combined in a single strain, resulting in a substantial shift in fermentation toward ethanol production. This double mutant produced 8.5-times more ethanol than wild-type cells growing on crystalline cellulose. Ethanol constituted 93% of the major fermentation products, corresponding to a molar ratio of ethanol to organic acids of 15, versus 0.18 in wild-type cells. During growth on acid-pretreated switchgrass, the double mutant also produced four times as much ethanol as wild-type cells. Detailed metabolomic analyses identified increased flux through the oxidative branch of the mutant's tricarboxylic acid pathway.</p> <p>Conclusions</p> <p>The efficient intron-based gene inactivation system produced the first non-random, targeted mutations in <it>C. cellulolyticum</it>. As a key component of the genetic toolbox for this bacterium, markerless targeted mutagenesis enables functional genomic research in <it>C</it>. <it>cellulolyticum </it>and rapid genetic engineering to significantly alter the mixture of fermentation products. The initial application of this system successfully engineered a strain with high ethanol productivity from cellobiose, cellulose and switchgrass.</p

Artificial Chiral Nanostructure at Oblique Incidence

International audienceWe propose in this paper the design of artificial nanostructure chirality obtained by oblique illumination. This structure is based on anisotropic metamaterial having an optical activity induced by the special geometry of the pattern and the incident beam. Starting from a non-chiral material, the artificial chirality is obtained thanks to the rectangular apertures which form the periodic perfect metal nanostructure (one layer) and the oblique incidence of the light beam. An extraordinary light transmission (93%) through the metal nanostructure is achieved by exciting the cavity modes. The extrinsic chirality obtained can be granted to the desired value by appropriately adjusting the geometric parameters and the angle of incidenc

Tunable artificial chirality with extraordinary transmission metamaterials

International audienceWe propose the design of a three-dimensional anisotropic chiral structure composed of double-layered metallic films. Each layer behaves as a half-wave plate thanks to the excitation and the propagation of guided modes inside the subwavelength apertures of each metallic layer. As in conventional optics, the optical rotation is tuned by simply changing the angle between the two plates. We numerically demonstrate that this property remains valid only if the whole second layer is rotated instead of twisting every pattern. Therefore, the plane of polarization can be rotated by any desired value and is accompanied by a transmission up to 80%. The proposed structure opens the way to the design of a new kind of chiral plate in the terahertz or microwave domains

Enhanced-transmission metamaterials as anisotropic plates

International audienceWe present an original design of anisotropic metamaterial plates exhibiting extraordinary transmission through perfectly conductor metallic screens perforated by a subwavelength double-pattern rectangular aperture array. The polarization properties of the fundamental guided mode inside the apertures are at the origin of the anisotropy. The metal thickness is a key parameter that is adjusted in order to get the desired value of the phase difference between the two transversal electromagnetic field components. As an example, we treat the case of a half-wave plate having 92% transmission coefficient. Such a study can be easily extended to design anisotropic plates operating in terahertz or microwave domains

Investigation of Losses in Fingers and Clamping Plates of High-Power Electrical Machines

International audienceWhen designing an electrical machine, the lossesin end-regions are often neglected or approximated withempirical equations due to the complexity of the involvedphysical phenomena and the difficulty to measure them. As aconsequence, important differences can appear between the totalmeasured losses and the value predicted by the analytic tools.This error can result in a high economic loss for machinemanufacturers. This paper presents a 3D FEM eddy current losscalculation in fingers and clamping plates of an experimentalbench set up. The study focuses on the effect of the axialcomponent of the flux density at the end region on these losses inthe case of different materials and power supply frequencies.Simulations results are presented and analyze

ORIENTAL JOURNAL OF CHEMISTRY Catecholase Activity Investigations using in situ Copper Complexes Continuing Schiff Base Derivatives with a Theoretical Calculation

ABSTRACT The study of catecholase activity of a series of Schiff base compounds using in situ copper complexes of 4-hydroxy-6-methyl-3-(1-(phenylimino)ethyl)-2H-pyran-2-one derivatives has been reported. The reaction rate depends on four parameters: The nature of the substitution in para position to the benzene ring, the nature of counter anion, the concentration of ligand and the nature of solvent. The highest rate activity is given by complex resulting from one equivalent of ligand L2 and two equivalents of copper acetate in methanol, which equal to 62.25 µmol.min .In other part, a theoretical study of such ligands using the semi-empirical method AM1 were also investigated. A good relationship founded between the maximal reaction rate (V max ) and the HOMO energy (Pearson correlation: r=-0.794)