Analyse Du Comportement Du Consommateur Du Carburant-Essence Au Cameroun: Examen Du Cas De La Ville De Maroua

The presence of violence or terrorism caused by the terrorist sect Boko Haram prompted the Nigerian Government to proceed with the closure of its border with the northern part of Cameroon This decision caused the rise in the price of adulterated fuel commonly known as zoua zoua in the local dialect which represents about 75 of the market for fuel consumed in the northern part of Cameroon In this context the main objective of this study is to analyze the behavior and sensitivity of the fuel-gasoline consumer in the city of Maroua The data used for this study come from a survey carried out by means of a questionnaire among 300 motorists with engines consuming only gasoline in the city of Maroua during the month of July 2019 This choice is justified by the unavailability of aggregate data on the volumes of fuel consumed in the city of Maroua and the concern to guarantee the size of the target sample To construct the sample the study used the non-random sampling method in this case the quota method Comparison of means tests on independent samples are used on cross-sectional data The results of the estimations obtained on primary data show that ceteris paribus the consumer turns to the informal sector and only turns away from it when the price of adulterated gasoline increase

Efficient extraction of the RuBisCO enzyme from spinach leaves using aqueous solutions of biocompatible ionic liquids

Ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCO) is the most abundant protein on the planet, being present in plants, algae and various species of bacteria, with application in the pharmaceutical, chemical, cosmetic and food industries. However, current extraction methods of RuBisCO do not allow high yields of extraction. Therefore, the development of an efficient and selective RuBisCOs’ extraction method is required. In this work, aqueous solutions of biocompatible ionic liquids (ILs), i.e., ILs derived from choline and analogues of glycine-betaine, were applied in the RuBisCO’s extraction from spinach leaves. Three commercial imidazolium-based ILs were also investigated for comparison purposes. To optimize RuBisCO’s extraction conditions, response surface methodology was applied. Under optimum extraction conditions, extraction yields of 10.92 and 10.57 mg of RuBisCO/g of biomass were obtained with the ILs cholinium acetate ([Ch][Ac]) and cholinium chloride ([Ch]Cl), respectively. Circular dichroism (CD) spectroscopy results show that the secondary structure of RuBisCO is better preserved in the IL solutions when compared to the commonly used extraction solvent. The obtained results indicate that cholinium-based ILs are a promising and viable alternative for the extraction of RuBisCO from vegetable biomass.publishe

Synthesis and characterization of analogues of glycine-betaine ionic liquids and their use in the formation of aqueous biphasic systems

A series of novel analogues of glycine-betaine ionic liquids (AGB-ILs), viz. 1-(4-ethoxy-4-oxobutyl)-1-methylpyrrolidin-1-ium, N,N,N-tri(n-butyl)(4-ethoxy-4-oxobutyl)-1-phosphonium and N,N,N-trialkyl(4-ethoxy-4-oxobutyl)-1-aminium cations with ethyl, n-propyl and n-butyl alkyl chains, combined with the bromide anion, have been synthesized and characterized. Their synthesis and characterization by spectroscopic methods and elemental analysis is here reported. These ILs were further characterized in what concerns their thermal properties and ecotoxicity against Allvibrio fischeri, and compared with the commercial tetra(n-butyl)ammonium and tetra(n-butyl)phosphonium bromide. The novel AGB-ILs described in this work have low melting points, below 100 °C, display high degradation temperatures (180–310 °C), and low toxicity as shown by being harmless or practically harmless towards the marine bacteria Allvibrio fischeri. Finally, the ability of the synthesized AGB-ILs to form aqueous biphasic systems with potassium citrate/citric acid (at pH 7) was evaluated, and the respective ternary phase diagrams were determined. It is shown that the increase of the cation alkyl chain length facilitates the creation of ABS, and that phosphonium-based ILs present a slightly better separation performance in presence of aqueous solutions of the citrate-based salt.publishe

Glycine-betaine-derived ionic liquids: Synthesis, characterization and ecotoxicological evaluation

Ionic Liquids (ILs) are generically regarded as environmentally "harmless" and thus, assumed as "non-toxic". However, due to the endless design possibilities, their ecotoxicological profile is still poorly known. An accurate knowledge on the toxicity of a substance is required, under the scope of environmental regulation worldwide, before their application and commercialization. Knowledge on the relationship between the chemical structure and toxic effects is essential for the future design of more biocompatible solvents. Focusing on the use of ILs as base lubricants, lubricant additives, or even as potential working fluids for absorption heat pumps, the knowledge on its environmental impact is of great importance, due to the possibility of spills. In this specific context, four analogues of glycine-betaine-based ILs (AGB-ILs) and four glycine-betaine based ILs (GB-ILs) were synthesized and characterized. Their ecotoxicity was assessed using representatives of two trophic levels in aquatic ecosystems, the bacteria Allivibrio fischeri (commonly used as a screening test organism) and the microalgae Raphidocelis subcapitata (as an alternative test organism that has been proven very sensitive to several IL families). The microalgae were more sensitive than the bacteria, hence, following a precautionary principle, we recommend considering the toxicity towards microalgae as an indicator in future studies regarding the focused ILs. Although four of the studied ILs were derived from a natural amino acid, all were considered hazardous for the aquatic environment, disproving the primary theory that all ILs derived from natural compounds are benign. Furthermore, the modification in the structure of anion and the cation can lead to the increase of toxicity.publishe

Sustainable strategies based on glycine–betaine analogue ionic liquids for the recovery of monoclonal antibodies from cell culture supernatants

Monoclonal antibodies (mAbs) are of crucial interest for therapeutic purposes, particularly in vaccination and immunization, and in the treatment of life-threatening diseases. However, their downstream processing from the complex cell culture media in which they are produced still requires multiple steps, making mAbs extremely high-cost products. Therefore, the development of cost-effective, sustainable and biocompatible purification strategies for mAbs is in high demand to decrease the associated economic, environmental and health burdens. Herein, novel aqueous biphasic systems (ABS) composed of glycine–betaine analogue ionic liquids (AGB-ILs) and K2HPO4/KH2PO4 at pH 7.0, the respective three-phase partitioning (TPP) systems, and hybrid processes combined with ultrafiltration were investigated and compared in terms of performance as alternative strategies for the purification and recovery of anti-human interleukin-8 (anti-IL-8) mAbs, which are specific therapeutics in the treatment of inflammatory diseases, from Chinese Hamster Ovary (CHO) cell culture supernatants. With the studied ABS, mAbs preferentially partition to the IL-rich phase, with recovery yields up to 100% and purification factors up to 1.6. The best systems were optimized in what concerns the IL concentration, allowing to take advantage of IL-based three-phase partitioning approaches where a precipitate enriched in mAbs is obtained at the ABS interface, yielding 41.0% of IgG with a purification factor of 2.7 (purity of 60.9%). Hybrid processes combining the two previous techniques and an ultrafiltration step were finally applied, allowing the recovery of mAbs from the different fractions in an appropriate buffer solution for further biopharmaceutical formulations, while allowing the simultaneous IL removal and reuse. The best results were obtained with the hybrid process combining TPP and ultrafiltration, allowing to obtain mAbs with a purity higher than 60%. The recyclability of the IL was additionally demonstrated, revealing no losses in the purification and recovery performance of these systems for mAbs. The biological activity of anti-IL-8 mAbs is maintained after the several purification and recovery steps, indicating that the novel ABS, three-phase partitioning and hybrid processes comprising AGB-ILs are promising and sustainable strategies in mAbs downstream processing.publishe

Complexes du cuivre, nickel et cobalt avec des bases de Schiff de type pyrrole-2-aldimine et etudes Redox

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79477 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Synthesis and characterisation of zinc(ii) complexes of tripodal N7 ligands involving pyridine and amine or amide nitrogen donors. Crystal structure of a zinc(ii) complex

International audienc

Complexes de cuivre, nickel et cobalt avec des ligands polyazotés pentadentés linéaires et heptadentés tripodes amido-pyridiniques et pyraziniques: synthèses, études thermodynamiques et structurales

Ce travail porte sur l étude de la coordination de cuivre, nickel et cobalt avec quatre nouveaux ligands polyazotés linéaires ou tripodes porteurs de groupements picolinamides ou pyrazinamides. L étude structurale par diffraction des rayons X des deux ligands tripodes montrent que leur réseau cristallin est stabilisé par des liaisons hydrogène intramoléculaires. En solution aqueuse, les titrages protométriques et spectrophotométriques ont permis de déterminer les constantes d acidité des ligands ainsi que les constantes globales de formation des complexes de cuivre et de nickel. Seuls les ligands porteurs de groupements picolinamides permettent la formation des complexes de type MLH ou ML ce qui montre que le noyau pyridinique se lie plus facilement que le noyau pyrazinique en milieu acide. La déprotonnation des groupements amidiques de ces ligands favorise dans tous les cas la mise en évidence des espèces mononucléaires [MLH-1]+, MLH-2 ou [MLH-3]- (M = Cu2+ ou Ni2+) alors que les complexes dinucléaires [Cu2LH-2]2+, [Cu2LH-3]+ et Cu2LH-4 sont obtenus uniquement avec le ligand tripode porteur de pyrazinamides. A l état solide, différents complexes de Cu(II), Ni(II) Co(II) et Co(III) dans lesquels le ligand est protonné, neutre ou déprotonné ont été synthétisés et caractérisés par les méthodes spectroscopiques (IR, UV-visible, RPE) ; seuls les ligands porteurs de picolinamides conduisent à des complexes où le ligand est protonné ou déprotonné. L étude radiocristallographique de trois complexes montre que pour certains composés la structure à l état solide peut être différente de celle obtenue en solution aqueuse.Four new linear or tripodal ligands providing pyridine-2-carboxamide or pyrazine-2-carboxamide moities were synthesized and the X ray crystal structures of the two tripodal ligands show that their crystal lattice is stabilized by intramolecular hydrogen bonds. Potentiometry and spectrophotometry studies, in aqueous solution allow the determination of the acidity constants of the ligands and the stability constants of the copper(II) and nickel(II) chelates. Only the two ligands providing pyridine-2-carboxamide moities allow the detection of [MLH]3+ and [ML]2+ species, indicating the more powerful coordinating ability of the pyridyl group than the pyrazyl group. The deprotonation of the amide groups of the ligands induce, in all the case, the formation of mononuclear [MLH-1]+, MLH-2 or [MLH-3]- species, whereas the tripodal ligand containing pyrazinamide groups allow the formation of dinuclear species [Cu2LH-2]2+, [Cu2LH-3]+ and [Cu2LH-4]. In solid state, different copper(II), nickel(II) and cobal(II) or cobalt(III) complexes with the protonated, neutral or deprotonated forms of the ligand have been prepared and characterized by spectroscopic techniques (IR, UV-Visible, EPR); only ligands containing picolinamide groups give complexes with protonated and deprotonated forms of the ligand. The crystal structure of three complexes investigated shows that, for some compounds, the environment of the metal ion for the species observed in aqueous solution could be different than those isolated in solid state.REIMS-BU Sciences (514542101) / SudocSudocFranceF