Current Issue Date 01-11-2018 to 31-01-2019
Fouda, S. Rashwan, A. El-Hossiany, F. E. El-Morsy
The effect of some corrosion inhibitors on the corrosion of Zn in 0.5 M HCl have been investigated by using mass loss (ML), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Polarization data clearly indicated that these compounds behaved as mixed type inhibitors. The effect of temperature on corrosion inhibition has been studied; the thermodynamic activation and adsorption parameters were calculated and discussed. EIS have used to investigate the mechanism of corrosion inhibition. The adsorption of these compounds on Zn was found to obey Langmuir adsorption isotherm. The surface morphology of the Zn specimens was evaluated using scanning electron microscope (SEM), Atomic Force Microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). Quantum chemical calculation was applied to elucidate the adsorption mode of inhibitors molecules onto Zn surface.
, Mamoudou Abdoul TOURE Elhadji Faye
Karaya gum or mbepp is produced by Sterculia setigera Del. in Africa. The value of the gum depends a lot on its viscosity and the absence of germs both of which are rarely studied. The objective of this study is to contribute to a better knowledge of the quality of karaya gum from Senegal. For this purpose, from gums originating from the region of Tambacounda, Senegal (i) the behavior of the viscosity of the gum as a function of the shear rate and (ii) the control of its microbiological quality were monitored. The viscosity of the two types of gum collected in the Bala, Daoudi and Malem Niani 1 sites (harvested during the hot dry period and one year old) and Malem Niani 2 (four months old and harvested during the dry-cool period) according to different shear rates has been studied. The results show that the viscosity of the S. setigera gum varies as a function of the interaction between the type of gum and the shear rate (p <0.0001). The mbepp gum collected at Daoudi and Malem Niani is free from Salmonella and Escherichia coli contamination. On the other hand, total mesophilic flora (on PCA) is very important (> 3,106). These results helped to acquire new knowledge and to identify Senegalese karaya gum (mbepp) as a good quality gum.
Mamoudou Abdoul TOURE , Elhadji Faye
La gomme karaya ou mbepp est produite par Sterculia setigera Del. en Afrique. La valeur de la gomme dépend beaucoup de sa viscosité et de l’absence de germes toutes deux rarement étudiées. L’objectif de cette étude est de contribuer à une meilleure connaissance de la qualité de la gomme karaya du Sénégal. Pour ce faire, à partir de gommes provenant de la région de Tambacounda, au Sénégal (i) le comportement de la viscosité de la gomme en fonction de la vitesse de cisaillement et (ii) le contrôle de sa qualité microbiologique ont été suivis. La viscosité des deux types de gommes collectées dans les sites de Bala, Daoudi et Malem Niani 1 (récoltées en période sèche-chaude et âgées d’un an) et Malem Niani 2 (âgée de quatre mois et récoltée en période sèche-fraîche) en fonction de différentes vitesses de cisaillement a été étudiée. Les résultats montrent que la viscosité de la gomme de S. setigera varie en fonction de l’interaction entre le type de gomme et la vitesse de cisaillement (p < 0,0001). La gomme mbepp récoltée à Daoudi et à Malem Niani, ne présente pas de contamination par les Salmonelles ou par Escherichia coli. Par contre, la flore totale mésophile (sur PCA) est très importante (> 3 106). Ces résultats ont permis d’acquérir de nouvelles connaissances et d’identifier la gomme karaya sénégalaise (mbepp) comme une gomme de bonne qualité.
S. Subedi and H. P. Lamichhane
Density Functional Theory (DFT) calculations have been carried out on a series of thirty two dipeptides and eleven tripeptides. Dipeptides were constructed by fixing cysteine at N-terminus/C-terminus and varying the remaining terminus with sixteen different amino acids. Tripeptides were constructed adding N- and C-terminus different amino acids in two sides of a cysteine. From the geometry optimization of these dipeptides and tripeptides, NT-CT combination (cysteine fixed at N-terminus and C-terminus group varying with different amino acids) of dipeptides, and the basis set 6-311G* gave more precise data than CT-NT combination (cysteine fixed at C-terminus and N-terminus group varying with different amino acids) of dipeptides and the basis set 6-31G*. To study the structural stability and sequence of amino acids in dipeptides and tripeptides, we have investigated the bond lengths and bond angles of amide plane. The absolute deviation obtained in the bond lengths of amide plane for dipeptides and tripeptides were calculated. The analysis of α-carbon bond angle angle resulted that the bond angle around the α-carbon of cysteine residue does not vary significantly, as only the maximum deviation of very small angle was seen in the case of dipeptide, but the bond angle around the α-carbon of varied amino acids showed a significant deviation. And, the bond angle around the α-carbon of tripeptide showed the significant deviation in the α-carbon bond angle of X- and Y-amino group. In conclusion, there is deviation of amide plane from planarity, which was drawn from the investigation of dihedral angle analysis of dipeptides and tripeptides. This deviation has been explained in terms of the combined effect of the hydrogen bonding within the dipeptide or tripeptide and the steric hindrance of the -R group of X-position or Y-position amino acid. In order to study internal barriers to the rotation, we have performed the potential energy scan of the optimized structure of cysteine residue by rotating three different groups separately: (a) amino (-NH2) group (b) carboxyl (-COOH) group and (c) -R (-CH2SH) group.
Song Guoqiang, Chen Yifa, Feng xiaoqing
A series of novel aryl amide analogues as PDE4 inhibitors were designed. Based on the crystal structure of phosphodiesterase IV subtype (PDE4) (PDB: 1XOQ), the Discovery Studio 4.5 software was used to screen the compounds by discovery studio docking. The result indicated that the 15 of the newly designed inhibitors have the most prospect and desired to be synthesized.
Abir Maazaoui, Asma Hrizi , and Moufida Romdhani-Younes
A simple and highly efficient synthesis of amino-β-hydroxysulfides has been carried out ring opening of epoxides with 2-aminobenzenethiol with catalytic amount of benzyl trimethylammonium hydroxide (Triton B) under solvent-free conditions. Excellent regioselectivity was achieved for aliphatic unsymmetrical epoxides, with nucleophilic attack at the less hindered carbon atom of the epoxide. In the case of styrene oxide the nucleophilic attack takes place exclusively on the more substituted carbon. This process was also regio- and chemo-selective as illustrated using epichlorohydrin with two epoxide ring positions and 2-aminobenzenethiol with two functional groups (SH and NH2).
P. Petrov and М. Marinov
Laboratory and semi industrial experiments for pyrometallurgical manufacturing of agglomerate from Obrochiste’s manganese concentrate (Dobrich province, Bulgaria) and deactivated vanadium catalyst (from the sulfuric acid production) in a Taman furnace and electric arc furnace are implemented. For a reducing agent are used carbon, aluminium and silicon plus aluminium. The coefficients of elements’ distribution between the metal and the slag phase for vanadium, manganese, iron, silicon, calcium, potassium, aluminium and magnesium are calculated.
Abir Maazaoui and Moufida Romdhani-Younes
Various β, β’-dihydroxythioethers, derived from oxirane were readily converted to their corresponding 1,5 bis-propargyloxy-sulfides, by treatment with propagyl bromide and Sodium hydride in anhydrous THF. These new compounds were obtained in good yields. This method is applicable to aliphatic, cyclic and aryl diols. The use of NaH allows the transformation of primary and secondary alcohols.