By using the Rayleigh-Schrödinger perturbation theory the rovibrational wave function is expanded in terms of the series of functions ϕ0,ϕ1,ϕ2,…ϕn, where ϕ0 is the pure vibrational wave function and ϕι are the rotational harmonics. By replacing the Schrödinger differential equation by the Volterra integral equation the two canonical functions α0 and β0 are well defined for a given potential function. These functions allow the determination of (i) the values of the functions ϕι at any points; (ii) the eigenvalues of the eigenvalue equations of the functions ϕ0,ϕ1,ϕ2,…ϕn which are, respectively, the vibrational energy Ev, the rotational constant Bv, and the large order centrifugal distortion constants Dv,Hv,Lv….. Based on these canonical functions and in the Born-Oppenheimer approximation these constants can be obtained with accurate estimates for the low and high excited electronic state and for any values of the vibrational and rotational quantum numbers v and J even near dissociation. As application, the calculations have been done for the potential energy curves: Morse, Lenard Jones, Reidberg-Klein-Rees (RKR), ab initio, Simon-Parr-Finlin, Kratzer, and Dunhum with a variable step for the empirical potentials. A program is available for these calculations free of charge with the corresponding author.
To search for newer and potent antileishmanial drugs, a series of 36 compounds of 5-(5-nitroheteroaryl-2-yl)-1,3,4-thiadiazole derivatives were subjected to a quantitative structure-activity relationship (QSAR) analysis for studying, interpreting, and predicting activities and designing new compounds using several statistical tools. The multiple linear regression (MLR), nonlinear regression (RNLM), and artificial neural network (ANN) models were developed using 30 molecules having pIC 50 ranging from 3.155 to 5.046. The best generated MLR, RNLM, and ANN models show conventional correlation coefficients R of 0.750, 0.782, and 0.967 as well as their leave-one-out cross-validation correlation coefficients RCV of 0.722, 0.744, and 0.720, respectively. The predictive ability of those models was evaluated by the external validation using a test set of 6 molecules with predicted correlation coefficients Rtest of 0.840, 0.850, and 0.802, respectively. The applicability domains of MLR and MNLR transparent models were investigated using William’s plot to detect outliers and outsides compounds. We expect that this study would be of great help in lead optimization for early drug discovery of new similar compounds.
Recent studies have focused on tailoring the catalytic currents of multicopper oxidase (MCO) enzymes-based biocathodes to enhance oxygen reduction. Biocathodes modified with natural substrates specific for MCO enzymes demonstrated drastic improvement for oxygen reduction. Performance of 1-pyrenebutanoic acid, succinimidyl ester (PBSE), and 2,5-dimethyl-1-phenyl-1H-pyrrole-3-carbaldehyde (Di-Carb) oriented bilirubin oxidase (BOx) modified gas diffusion biocathode has been highly improved by incorporating hematin, a porphyrin precursor as electron transfer enhancement moiety. Hematin modified electrodes demonstrated direct electron transfer reaction of BOx exhibiting larger O 2 reduction in current density in phosphate buffer solution (pH 7.0) without the need of a mediator. A remarkable improvement in the catalytic currents with 2.5-fold increase compared to non-hematin modified oriented BOx electrodes was achieved. Moreover, a mediatorless and compartmentless glucose/O 2 biofuel cell based on DET-type bioelectrocatalysis via the BOx cathode and the glucose dehydrogenase (GDH) anode demonstrated peak power densities of 1 mW/cm 2 at pH 7.0 with 100 mM glucose/10 mM NAD fuel. The maximum current density of 1.6 mA/cm 2 and the maximum power density of 0.4 mW/cm 2 were achieved at 300 mV with nonmodified BOx cathode, while 3.5 mA/cm 2 and 1.1 mW/cm 2 of current and power density were achieved with hematin modified cathode. The performance improved 2.4 times which attributes to the hematin acting as a natural precursor and activator for BOx activity enhancement.
Cathodic electrochemical deposition (CED) is introduced as an efficient and effective method for synthesis and surface coating of superparamagnetic iron oxide nanoparticles (SPIONs). In this way, bare Fe3O4 nanoparticles were electrosynthesized through CED method from aqueous solution Fe3+ : Fe2+ chloride (molar ratio of 2 : 1). In the next step, the surface of NPs was coated with polyethyleneimine (PEI) and polyethylene glycol (PEG) during the CED procedure, and PEG/PEI coated SPIONs were obtained. The prepared NPs were evaluated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), vibrating sample magnetometer (VSM), and field-emission scanning electron microscopy (FE-SEM). The pure magnetite phase and nanosize (about 15 nm) of the prepared NPs were confirmed by XRD and FE-SEM. The presence of two coats (i.e., PEG and PEI) on the surface of electrosynthesized NPs was proved via FTIR results. The percentage of polymer coat (37.5%) on the NPs surface was provided by TGA analysis. The high magnetization value, negligible coercivity, and remanence measured by VSM indicate the superparamagnetic nature of both prepared NPs. The obtained results confirmed that the prepared Fe3O4 nanoparticles have suitable physicochemical and magnetic properties for biomedical applications.
In this work, we synthesized In2S3 powder through chemical bath deposition method (CBD) in acid medium; we used thioacetamide as sulphide source and InCl3 as indium ion source. X-ray diffraction, diffuse reflection, and Raman spectroscopy measurements were used for In2S3 powder physicochemical characterization. Optical analysis indicated that In2S3 was active in the visible region of electromagnetic spectrum; it had a band gap of 2.47 eV; the diffraction patterns and Raman spectroscopy suggested that powder had polycrystalline structure. Furthermore, we also studied the adsorption process of methylene blue (MB) on In2S3 powder; adsorption studies indicated that the Langmuir model describes experimental data. Finally, photocatalytic degradation of MB was studied under visible irradiation in aqueous solution; besides, pseudo-first-order model was used to obtain kinetic information about photocatalytic degradation; results indicated that the powder catalyst reduces 26% concentration of MB under visible irradiation.
(E)-N-Aryl-2-ethene-sulfonamide and its derivatives are potent anticancer agents; these compounds inhibit cancer cells proliferation. A study of quantitative structure-activity relationship (QSAR) has been applied on 40 compounds based on (E)-N-Aryl-2-ethene-sulfonamide, in order to predict their anticancer biological activity. The principal components analysis is used for minimizing the base matrix and the multiple linear regression (MLR) and multiple nonlinear regression have been used to design the relationships between the molecular descriptor and anticancer properties of the sulfonamide derivatives. The validation of the models MLR and MNLR has been done by dividing the dataset into training and test set, the external validation of multiple correlation coefficients was RpIC50 = 0.81 for MLR and RpIC50 = 0.91 for MNLR. The artificial neural network (ANN) showed a correlation coefficient close to 0.96, which concluded that this latter model is more effective and much better than the other models. This obtained model (ANN) has been confirmed by two methods of LOO cross-validation and scrambling (or Y-randomization). The high correlation between experimental and predicted activity values was observed, indicating the validation and the good quality of the derived QSAR model.
In this work, we fabricated system In(O,OH)S/i-ZnO/n+-ZnO to be used as potential optical window in thin films solar cells. i-ZnO/n+-ZnO thin films were synthesized by reactive evaporation (RE) method and In(O,OH)S thin films were synthesized by chemical bath deposition (CBD) method; all thin films were deposited on soda lime glass substrates. Thin films were characterized through X-ray diffraction (XRD), atomic force microscopy (AFM), and spectral transmittance measurements. Structural results indicated that both thin films were polycrystalline; furthermore, morphological results indicated that both thin films coated uniformly soda lime glass substrate; besides, optical characterization indicated that system had more than 80% of visible radiation transmittance.
Lawsonia inermis also known as henna was studied as a corrosion inhibitor for aluminum alloy in seawater. The inhibitor has been characterized by optical study via Fourier transform infrared spectroscopy (FTIR). The FTIR proves the existence of hydroxyl and carbonyl functional groups in Lawsonia inermis . Aluminum alloy 5083 immersed in seawater in the absence and presence of Lawsonia inermis was tested using electrochemistry method, namely, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP). EIS and PP measurements suggest that the addition of Lawsonia inermis has caused the adsorption of inhibitor on the aluminum surface. The adsorption behavior of the inhibitor follow Langmuir adsorption model where the value of free energy of adsorption, -ΔG, is less than 40 kJ/mol indicates that it is a physical adsorption. Finally, it was inferred that Lawsonia inermis has a real potential to act as a corrosion inhibitor for aluminum alloy in seawater.
A homologous series of liquid crystal bearing with heterocyclic thiophene Schiff base ester with alkanoyloxy chain (CH3(CH2)nCOO–, where n=4, 6, 8, 10, 12, 14, 16) was successfully synthesized through the modification of some reported methods. The structural information of these compounds was isolated and characterized through some spectroscopic techniques, such as FTIR, 1H, and 13C NMR and elemental analysis. Textural observation was carried out using a polarizing optical microscope (POM) over heating and cooling cycles. It was found that all synthesized compounds (3a–g) exhibited an enantiotropic nematic phase upon the heating and cooling cycle with high thermal stability. Moreover, a characteristic bar transition texture was observed for compounds 3f and 3g which have shown transition of nematic-to-smectic C phase. This has been further confirmed by obtaining relative phase transition temperature using the differential scanning calorimetry (DSC).
Heat of formation is one of several important parameters used to assess the performance of energetic compounds. We evaluated the ability of six different methods to accurately calculate gas-phase heat of formation (ΔfH298,go) values for a test set of 45 nitrogen-containing energetic compounds. Density functional theory coupled with the use of isodesmic or other balanced equations yielded calculated results in which 82% (37 of 45) of the ΔfH298,go values were within ±2.0 kcal/mol of the most recently recommended experimental/reference values available. This was compared to a procedure using density functional theory (DFT) coupled with an atom and group contribution method in which 51% (23 of 45) of the ΔfH298,go values were within ±2.0 kcal/mol of these values. The T1 procedure and Benson’s group additivity method yielded results in which 51% (23 of 45) and 64% (23 of 36) of the ΔfH298,go values, respectively, were within ±2.0 kcal/mol of these values. We also compared two relatively new semiempirical approaches (PM7 and RM1) with regard to their ability to accurately calculate ΔfH298,go. Although semiempirical methods continue to improve, they were found to be less accurate than the other approaches for the test set used in this investigation.
A systematic computational investigation of hydrogen abstraction by OH from the full series of fluorinated ethyl methyl ethers (EME) containing at least one H and one F, C2HnX5-nOCHmX3-m (n=0–5, m=0–3; and n=m=0 not allowed), including 147 reactants and 469 transition states, has been carried out, employing the MP2/6-31G(d) level of theory. Results for optimized geometries, including evidence of intramolecular hydrogen bonding in transition states, and barrier heights are presented. Trends pertaining to the number of fluorines substituted, key bond lengths, barrier heights, and key bond angles were found with good correlations and were investigated. An increase in the number of F increases the barrier height of the reaction. An increase in some parameters such as C–H length of TS, relative change in C–H from reactants to TS, ∠COC of reactants, ∠HOH in the TS, and relative change in ∠HOH between TS and free water bond angle also correlates with increased barrier height. An increase in other parameters like C–H length in the reactants and hydrogen bonding can decrease the barrier height.
We present explicit formula for the general Randić connectivity, general sum-connectivity, Hyper-Zagreb and Harmonic Indices, and Harmonic polynomial of some simple connected molecular graphs.
Theoretical description of the metastable phase decay kinetics in the presence of specific connections between the embryos of small sizes has been given. The theory of the decay kinetics in the presence of relaxation processes is constructed in analytical manner. The m-mers nucleation is investigated and the global kinetics of decay is also constructed in this case analytically.
The ability of gum exudates ofAzadirachta indica(GAI) to inhibit corrosion on mild steel in 1 mol L−1HCl has been studied using mass loss, polarization, and impedence measurements. The effect of temperature (303–323 K) and immersion time of 1, 2, 4, 6, and 12 hours on corrosion behavior of mild steel was examined. Gum exudates decrease the corrosion rate up to a concentration of 80 ppm and at 323 K temperature. GAI adsorb chemically onto the surface of the mild steel while it obeys Langmuir adsorption isotherms. Polarization studies show GAI as mixed mode inhibitor. Surface studies ascertain that a shielding layer was formed on the mild steel surface.
In a search of newer and potent antileishmanial (against promastigotes and amastigotes form of parasites) drug, a series of 60 variously substituted acridines derivatives were subjected to a quantitative structure activity relationship (QSAR) analysis for studying, interpreting, and predicting activities and designing new compounds by using multiple linear regression and artificial neural network (ANN) methods. The used descriptors were computed with Gaussian 03, ACD/ChemSketch, Marvin Sketch, and ChemOffice programs. The QSAR models developed were validated according to the principles set up by the Organisation for Economic Co-operation and Development (OECD). The principal component analysis (PCA) has been used to select descriptors that show a high correlation with activities. The univariate partitioning (UP) method was used to divide the dataset into training and test sets. The multiple linear regression (MLR) method showed a correlation coefficient of 0.850 and 0.814 for antileishmanial activities against promastigotes and amastigotes forms of parasites, respectively. Internal and external validations were used to determine the statistical quality of QSAR of the two MLR models. The artificial neural network (ANN) method, considering the relevant descriptors obtained from the MLR, showed a correlation coefficient of 0.933 and 0.918 with 7-3-1 and 6-3-1 ANN models architecture for antileishmanial activities against promastigotes and amastigotes forms of parasites, respectively. The applicability domain of MLR models was investigated using simple and leverage approaches to detect outliers and outsides compounds. The effects of different descriptors in the activities were described and used to study and design new compounds with higher activities compared to the existing ones.
A polymeric thin film modified electrode, that is, poly(niacinamide) modified carbon paste electrode (MCPE), was developed for the electrochemical determination of catechol (CC) by using cyclic voltammetric technique. Compared to bare carbon paste electrode (BCPE), the poly(niacinamide) MCPE shows good electrocatalytic activity towards the oxidation of catechol in phosphate buffer solution (PBS) of physiological pH 7.4. All experimental parameters were optimized. Poly(niacinamide) modified carbon paste electrode gave a linear response between concentration of CC and its anodic peak current in the range within 20.6–229.0 μ M. The limit of detection (3S/M) and limit of quantification (10S/M) were 1.497 μ M and 4.99 μ M, respectively. From the study of scan rate variation, the electrode process was found to be adsorption-controlled. The involvement of protons and electrons in the oxidation of CC was found to be equal. The probable electropolymerisation mechanism of niacinamide was proposed. Finally, this method can be used in development of a sensor for sensitive determination of CC.
We apply density functional theory at PBE/6-311G(d) level as well as nonorthogonal tight-binding model to study the Stone-Wales transformation in C-36 fullerene embedded inside the (14,0) zigzag carbon nanotube. We optimize geometries of two different isomers with the D-2d and the D-6h symmetries and the transition state dividing them. The mechanism of Stone-Wales transformation from D-2d to D-6h symmetry for the encapsulated C-36 is calculated to be the same as for the isolated one. It is found that the outer carbon wall significantly stabilizes the D-6h isomer. However, carbon nanotube reduces the activation barrier of Stone-Wales rearrangement by 0.4 eV compared with the corresponding value for the isolated C-36.
The removal of toxic dye rhodamine B (RB) from aqueous solution was achieved by using Casuarina equisetifolia cone (CEC) as an adsorbent. Batch experiment method was used in order to investigate the effects of contact time, pH, temperature, ionic strength, and dye concentration on the adsorption process. Kinetics and isotherm theoretical models were applied on the experimental data and it was found that the pseudo-2nd-order kinetics and the Langmuir isotherm model best fitted into the data. The Langmuir maximum adsorption capacity for CEC was determined as 49.5 mg g −1 . The adsorption of RB onto CEC is thermodynamically favourable, feasible, and endothermic in nature.
The industrial waste, bauxite residue generated in the Bayer chemical process of alumina production, commonly known as red mud (RM) has been used as the adsorbent for selective removal of phosphate in aqueous solutions. RM collected from the storage area of alumina industry was characterized by chemical analysis and physical methods such as BET surface area, Scanning Electron Microscopy (SEM), particle size analysis, and X-ray diffraction (XRD) methods. Among the various red mud samples (0.2–200 μ ) studied, the samples treated with 1 M HCl for 2 h were found better for the selective adsorption of phosphate in comparison with untreated and heat treated RM samples. The presence of phosphate in the aqueous samples collected after adsorption studies with red mud was determined by standard spectrophotometric procedure using ammonium molybdate and ascorbic acid in nitrate medium at λmax 880 nm. The studies reported significant adsorption of phosphate on acid treated red mud in comparison with adsorption of phosphate on untreated and heat treated red mud, respectively. The adsorption of phosphate on raw red mud and activated red mud was further investigated with respect to stirring time, pH of the solution, dose of adsorbent, and varying phosphate concentration. Acid treated RM is observed as an efficient and cost-effective adsorbent for selective removal of phosphate in aqueous solutions.
The oxidation kinetics of fluorenone hydrazone (FH) using potassium permanganate in alkaline medium were measured at a constant ionic strength of 0.1 mol dm −3 and at 25°C using UV/VIS spectrophotometer. A first-order kinetics has been monitored in the reaction of FH with respect to [permanganate]. Less-than-unit order dependence of the reaction on [FH] and [OH − ] was revealed. No pronounced effect on the reaction rate by increasing ionic strength was recorded. Intervention of free radicals was observed in the reaction. The reaction mechanism describing the kinetic results was illustrated which involves formation of 1 : 1 intermediate complex between fluorenone hydrazones and the active species of permanganate. 9H-Fluorenone as the corresponding ketone was found to be the final oxidation product of fluorenone hydrazone as confirmed by GC/MS analysis and FT-IR spectroscopy. The expression rate law for the oxidation reaction was deduced. The reaction constants and mechanism have been evaluated. The activation parameters associated with the rate-limiting step of the reaction, along with the thermodynamic quantities of the equilibrium constants, have been calculated and discussed.
