A Study of the Electrochemical Behavior of Copper in Acid Medium in Presence of Some Organic Amine Compounds

The rate of corrosion of copper metal in presence of methyl amine, dimethyl amine, diethyl amine, triethyl amine, diethanol amine, and triethanol amine determined by measuring the anodic limiting current. The factors used are type of organic amine compounds and its concentration, concentration of H₃Po₄, viscosity of solution, density, diffusion coefficient, and rate of rotation. It has been found that, the rate of corrosion decrease in presence of these compounds. The inhibition percentage ranged from 9.72% to 80.14% depending on the type of inhibitor and its concentration. It is suggested that the decrease in the rate of corrosion is attributed to the increase in interfacial viscosity of the solution and decrease the diffusion coefficient of the copper ion. It has been found that we can apply the Langmuir, Flory-Huggins, and kinetic adsorption isotherms. It has been found that the rate of inhibition is increases in order: methyl amine, dimethyl amine, diethyl amine, triethyl amine, diethanol amine, and triethanol amine. The rate of corrosion depends on the H₃Po₄ concentration as well as on the electrode height. The limiting current in undivided cells is higher than in divided cells due to the uprising H₂ bubbles, which enhances the rate of corrosion. Also, the rate of corrosion was found to increase by increasing the speed of rotating electrode. The dimensionless groups were calculated, and the relation between them was given and the equation given as following: Sh = 0.5046 Re^0.7201(Sc)^0.33 for methyl amine; Sh = 0.5381 Re^0.7157(Sc)^0.33 for dimethyl amine; Sh = 0.4887 Re^0.7356(Sc)^0.33 for diethyl amine; Sh = 0.5167 Re^0.7207(Sc)^0.33 for triethyl amine; Sh = 0.5373 Re^0.7238(Sc)^0.33 for diethanol amine; and Sh = 0.4958 Re^0.7280(Sc)^0.33 for triethanol amine.     

Etude de la Reactivite Entre L'orthophosphate Tricalcique Apatitique et L'oxalate de Calcium

Several difficulties arise when studying the mineral component of calcified tissues: This material is complex due to the large number of atomic components, its heterogeneous composition, and varying factors. It is linked strongly to the organic component, and today no available technique allows a complete separation of these two components without alteration of one of them. In the present work the interaction of apatitic calcium phosphate with calcium oxalate has been studied. By heating stoechiometric amounts of these two solids, it was found that the presence of CO 3 2 m and CaO produced by calcium oxalate induces a decrease in P 2 O 7 4 m arising from HPO 4 2 m content of apatitic calcium phosphate. L'étude physico-chimique de la partie minérale des tissus calcifiés est extrêmement étendue et complexe. Fortement liée à des composés organiques, des difficultés de séparation, d'identification et d'étude du comportement de ces matériaux ont été signalées par de nombreux auteurs. En vue d'identifier l'effet des ions carbonate CO 3 2 m et du CaO sur la détermination de la teneur des ions (HPO 4 2 m ) des apatites synthétiques, les interactions entre le phosphate tricalcique apatitique et l'oxalate de calcium ont été étudiées. Il a été constaté que les ions CO 3 2 m produits par le carbonate de calcium issu de l'oxalate de calcium, conduisent à une diminution relative de la teneur des ions P 2 O 7 4 m (provenant des ions HPO 4 2 m ) dans le mélange équimolaire de phosphate apatitique et d'oxalate de calcium, dans le domaine de températures 400-520°;C. Au-delà de 520°;C la seconde diminution de la teneur des ions P 2 O 7 4 m est attribuée aux interactions des ions P 2 O 7 4 m et du CaO.     

Redox Mechanism and Evaluation of Kinetic and Thermodynamic Parameters of 1,3‐Dioxolo[4,5‐g]pyrido[2,3‐b]quinoxaline Using Electrochemical Techniques

The electrochemical behavior of a biologically important heterocyclic compound, 1,3‐dioxolo[4,5‐g]pyrido[2,3‐b]quinoxaline was investigated by cyclic, square wave and differential pulse voltammetry in solutions of different pH. Kinetic and thermodynamic parameters like standard rate constant, diffusion coefficient, apparent energy of activation_, standard Gibbs free energy and enthalpy and entropy changes were evaluated. Limits of detection and quantification were determined by square wave voltammetry. The redox mechanism of the compound was proposed on the basis of experimental results. Computational chemistry was used as a tool for the verification of experimental outcomes and assessment of different theoretical parameters     

Synthesis of Some New Heterocycles Derived from Ethyl 7‐Amino‐3‐(3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazolin‐4‐yl)‐5‐aryl‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxylate of Biological Importance

Ethyl 7‐amino‐3‐(3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazolin‐4‐yl)‐5‐aryl‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxylate was synthesized by the reaction of 4‐(2‐aminothiazol‐4‐yl)‐3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazoline with arylidene ethyl cyanoacetate and it transformed to related fused heterocyclic systems via reaction with various reagents. The biological activities of these compounds were evaluated.     

Potential Use of Propolis in Phytocosmetic as Phytotherapeutic Constituent

Phytocosmetic is an important aspect of traditional medicine in several cultures. Researchers are now focusing to find new and effective ingredients of natural origin. Propolis is a natural beehive product extensively used in traditional medicine. We aimed in the present study to investigate the potential use of propolis as an aesthetic and phytotherapeutic constituent in phytocosmetics. Propolis was extracted using 80% ethanol. Total phenolic and flavonoid contents were determined calorimetrically. Free radical scavenging ability and reducing capacity were evaluated using four assays and expressed as IC₅₀ values. Antibacterial activity was evaluated by the determination of minimum inhibitory concentration (MIC) on 11 Gram-positive and Gram-negative bacteria. The wound healing activity of 30% ethanolic extract and propolis ointment was studied using excision wounds in the anterio-dorsal side of the rats. The phenolic acid composition of the tested propolis was investigated using UFLC/MS-MS analysis. The tested propolis was rich in phenolic and flavonoid content and demonstrated an interesting antibacterial and antioxidant activity. Wounds treated with propolis appear to display a lesser degree of inflammation. Chemical analysis led to the identification of 11 phenolics. Among them, five are considered as main compounds: Chlorogenic acid (48.79 ± 5.01 ng/mL), Gallic acid (44.25 ± 6.40 ng/mL), Rutin (21.12 ± 3.57 ng/mL), Caffeic acid (28.19 ± 4.95 ng/mL), and trans-cinnamic acid (20.10 ± 6.51 ng/mL). Our results indicated that propolis can not only be used as a cosmetic ingredient but also be used as a preventative and curative constituent, which might be used as a barrier when applied externally on infected and non-infected skin.     

Biological Efficacy of Compounds from Stingless Honey and Sting Honey against Two Pathogenic Bacteria: An In Vitro and In Silico Study

Honey inhibits bacterial growth due to the high sugar concentration, hydrogen peroxide generation, and proteinaceous compounds present in it. In this study, the antibacterial activity of stingless and sting honey against foodborne pathogenic bacteria isolated from spoiled milk samples was examined. The isolated bacterial strains were confirmed as Bacillus cereus and Listeria monocytogenes through morphological, biochemical, and 16 s RNA analysis. Physiochemical characterizations of the honey samples revealed that both of the honey samples had an acidic pH, low water content, moderate reducing sugar content, and higher proline content. Through the disc diffusion method, the antibacterial activities of the samples were assayed and better results were observed for the 50 mg/disc honey. Both stingless and sting honey showed the most positive efficacy against Bacillus cereus. Therefore, an in silico study was conducted against this bacterium with some common compounds of honey. From several retrieved constituents of stingless and sting honey, 2,4-dihydroxy-2,5-dimethyl 3(2H)-furan-3-one (furan) and 4H-pyran-4-one,2,3-dihydro of both samples and beta.-D-glucopyranose from the stingless revealed high ligand-protein binding efficiencies for the target protein (6d5z, hemolysin II). The root-mean-square deviation, solvent-accessible surface area, the radius of gyration, root-mean-square fluctuations, and hydrogen bonds were used to ensure the binding stability of the docked complexes in the atomistic simulation and confirmed their stability. The combined effort of wet and dry lab-based work support, to some extent, that the antimicrobial properties of honey have great potential for application in medicine as well as in the food industries.     

Paramagnetic pyrrole-based semiconductor molecular material

The electrochemical oxidation of hexa-N-pyrrolylbenzene in organic media leads, via intramolecular coupling of the pyrrole residues, to the deposition of a molecular semiconductor film on an electrode surface. In situ electron spin resonance–electrochemical experiments reveal that the semiconductor is endowed with both properties of conducting polymers (i.e., reversible oxidation) and polyaromatic molecular materials (i.e., highly paramagnetic). The material, which is easy to process as soft homogeneous thin film, shows a tunable 0 to 1 spin concentration per molecule at room temperature by controlling the electrochemical potential. Contribution to the Fall Meeting of the European Materials Research Society, Symposium D: 9th International Symposium on the Electrochemical–Chemical Reactivity of Metastable Materials, Warsaw, 17th–21st September, 2007. An erratum to this article can be found at     

Fuzzy subgroups of nilpotent groups

In 1991, Asaad has suggested the following question: What can be said about the structure of a group G when information is known about the structure of a fuzzy subgroup A of G and vice-versa? This question has been partially investigated in Fuzzy Sets and Systems39 (1991) 323–328. The purpose of this paper is to continue more investigations for the above mentioned question.     

(o-Hydroxyphenyl)methylphosphonic acids: Synthesis and potentiometric determinations of their pKa Values

(o-Hydroxyphenyl)methylphosphonic acids are readily obtained from o-(bromomethyl)- or o-(hydroxymethyl)phenols and trialkyl phosphites. Subsequent hydrolysis leads to the corresponding phosphonic acids. For a series of such compounds, the pK_a values have been determined by potentiometry. Their dependence on additional substituents in the aromatic ring is discussed in terms of electronic and steric effects.