The role of detoxifying enzymes in the resistance of the cowpea aphid (Aphis craccivora Koch) to thiamethoxam

The cowpea aphid (Aphis craccivora Koch) is considered a serious insect pest attacking several crops. We carried out biochemical studies to elucidate the role of the metabolising enzymes in conferring resistance to thiamethoxam, in two strains (resistant and susceptible) of the cowpea aphid. Bioassay experiments showed that the thiamethoxam selected strain developed a 48 fold resistance after consecutive selection with thiamethoxam for 12 generations. This resistant strain also exhibited cross-resistance to the tested carbamates; pirimicarb and carbosulfan, organophosphorus (malathion, fenitrothion, and chlorpyrifos-methyl), and the neonicotinoid (acetamiprid). Synergism studies have indicated that S,S,S-tributyl phosphorotrithioate (DEF), a known inhibitor for esterases, increased thiamethoxam toxicity 5.58 times in the resistant strain compared with the susceptible strain. Moreover, the biochemical determination revealed that carboxylestersae activity was 30 times greater in the resistant strain than in the susceptible strain. In addition, the enzyme activity of glutathione S-transferase (GST) and mixed function oxidases (mfo) increased only in the resistant strain 3.7 and 2.7 times, respectively, in relation to the susceptible (the control). Generally, our results suggest that the higher activity of the detoxifying enzymes, particularly carboxylesterase, in the resistant strain of the cowpea aphid, apparently have a significant role in endowing resistance to thiamethoxam, although additional mechanisms may contribute

Novel cationic surfactants from fatty acids and their corrosion inhibition efficiency for carbon steel pipelines in 1 M HCl

Four fatty acids were used as a source of alkyl halides. Untraditionally tertiary amines were prepared by ethoxylation of aromatic and aliphatic fatty amines. These alkyl halide and tertiary amines were used to prepare 20 cationic quaternary ammonium surfactants (QASS). Their chemical structures were characterized and they tested as corrosion inhibitors for carbon steel in 1 M HCl solution. The corrosion inhibition efficiency was measured using, weight loss and potentiodynamic polarization methods. The inhibition efficiencies obtained from the two employed methods are nearly closed. From the obtained data it was found that, the inhibition efficiency increases with increasing the inhibitor concentration until the optimum one. Also, it was found that the inhibition efficiency of QASs which based on ethoxylated aromatic tertiary amine is greater than the obtained efficiencies by the QASs which based on ethoxylated aliphatic tertiary amines. The QASs based on alkyl halide C16 exhibited the maximum inhibition efficiency 98.8%. Adsorption of the inhibitors on the carbon steel surface was found to obey Langmuir’s adsorption isotherm. The quantum chemical calculations were done for some selected quaternary ammonium compounds based on their chemical structures QL1,4,5–QP3,4,5. The following quantum chemical indices such as the bond length, bond angle, charge density distribution, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), energy gap ΔE = HOMO − LUMO, and dipole moment (u) were considered. The relation between these parameters and the inhibition efficiencies was explained on the light of the chemical structure of the used inhibitors

Efficient methodology for the preparation and fabrication of cation exchange membranes using trichloroacetic acid and cellulose biopolymer

This article presents a new method for preparing enhanced cation exchange membrane (CEM) for water treatment using cellulose biopolymer. The preparation methodology of CEM membranes was performed in two steps; functionalization followed by fabrication. Firstly, cellulose powder was functionalized with trichloroacetic acid at different reaction times to prepare carboxymethyl tricellulose (CMTC). In the second step, the exchange memberane was fabricated via phase inversion technique using the functionalized cellulosic material and polyethylene glycol as a pore former. The prepared CEM was fully characterized using FTIR, SEM, mechanical properties, and degree of substitution (DS) determination. The morphological microstructure of the CEM membrane was investigated and discussed. The microstructural analysis by FTIR confirmed the functionalization process. The tensile values obtained at different reaction times showed the effectiveness of using trichloroacetic acid in the carboxymethylation and consequently, the stability of the obtained functionalized cellulose. The obtained DS values are higher than that of the commercial CMC and also the published values. It has been observed that the prepared CEM have an average DS value of 1.5 and therefore much higher than the DS value of commercial CMC whose DS ranges between 0.7 and 1.2. The prepared CEM membranes were morphologically investigated by SEM. The SEM photos showed homogeneously distributed small pores on the entire surface of the membrane, and its cross-section is a multilayer with large pores