Toxicity of individual and mixture of organic compounds to P. Phosphoreum and S. Capricornutum using interpretable simple structural parameters.

Human and environmental ecosystem beings are exposed to multicomponent compound mixtures but the toxicity nature of compound mixtures is not alike to the individual chemicals. This work introduces four models for the prediction of the negative logarithm of median effective concentration (pEC50) of individual chemicals to marine bacteria Photobacterium Phosphoreum (P. Phosphoreum) and algal test species Selenastrum Capricornutum (S. Capricornutum) as well as their mixtures to P. Phosphoreum, and S. Capricornutum. These models provide the simplest approaches for the forecast of pEC50 of some classes of organic compounds from their interpretable structural parameters. Due to the lack of adequate toxicity data for chemical mixtures, the largest available experimental data of individual chemicals (55 data) and their mixtures (99 data) are used to derive the new correlations. The models of individual chemicals are based on two simple structural parameters but chemical mixture models require further interaction terms. The new model's results are compared with the outputs of the best accessible quantitative structure-activity relationships (QSARs) models. Various statistical parameters are done on the new and comparative complex QSAR models, which confirm the higher reliability and simplicity of the new correlations.

The use of simple structural parameters of organic compounds to assess their PUF-air partition coefficients.

A novel approach is introduced for the reliable prediction of PUF-air partition coefficients of organic compounds, which can determine the environmental fate of organic compounds during interactions with air, soil, and water. The biggest accessible measured data of PUF-air partition coefficients for 170 chemicals are used to develop and test the novel model. In comparison to available quantitative structure-property relationship (QSPR) methods for the prediction of PUF-air partition coefficients that need complex descriptors, the here used descriptors are simpler. The assessed various statistical factors of the simple method containing 147 (training) and 23 (test) organic compounds can verify the external and internal cross-validations. Various statistical parameters confirm the high reliability of the novel model as compared with the outputs of complex multiple linear regression (MLR), artificial neural network (ANN) and support vector machine (SVM) methods. The values of R-squared (R2), and root mean square error (RMSE) of the new model are for training/test sets are 0.924/0.894 and 0.374/0.318, respectively. Meanwhile, R2 and RMSE values for three comparative models training/test sets are (i) MLR: 0.848/0.670 (R2) and 0.531/0.573 (RMSE); (ii) ANN: 0.902/0.664 (R2) and 0.425/0.560 (RMSE); (iii) SVM: 0.935/0.794 (R2) and 0.351/0.419 (RMSE). Thus, the new model the simplest approach with higher reliability in comparison to the best available methods.

A novel approach for assessment of antitrypanosomal activity of sesquiterpene lactones through additive and non-additive molecular structure parameters.

Human African trypanosomiasis (HAT) or sleeping sickness is a protozoan neglected tropical disease, which is the main health worry in more than 20 countries in Africa. A novel approach is presented to predict the antitrypanosomal activity of sesquiterpene lactones (STLs) in terms of biological activity (pIC50). The largest reported data set of pIC50 for Trypanosoma brucei rhodesiense (Tbr) as one form of HAT are used to derive and test the new model. The new model is based on five additive and two non-additive molecular structural parameters in several frameworks where it can be easily applied through a computer code. It is derived and tested based on 125 and 31 experimental data, respectively, with different types of statistical parameters. The high reliability of the novel model is compared with the best available QSAR models, which use "classical" molecular descriptors, and 3D pharmacophore features. The values of R2 (correlation coefficient), root mean squared error (RMSE), and RMSEP (root mean square error of prediction) of the new model are 0.77, 0.38, and 0.35, respectively. Meanwhile, R2, RMSE, and RMSEP of comparative QSAR models based on complex descriptors are in the ranges 0.71-76, 0.46-0.4, and 0.51-0.44, respectively. The predictive results of the novel approach confirm its high simplicity, reliability, precision, accuracy, and goodness-of-fit.

Simple method for assessment of activities of thrombin inhibitors through their molecular structure parameters.

Thrombi (blood clots) form in blood vessels in thromboembolic disorders, which are among the main reasons for death in the world. A novel approach is presented to predict thrombin inhibitory activities ((log(103/Ki) (nM)) of some classes of non-peptidic thrombin inhibitors. The largest reported data set of log(103/Ki) for 260 thrombin inhibitors are used to derive and test the new model where it can be easily applied through a computer code. The new model is derived and tested based on 201 and 59 experimental data, respectively, where its reliability is established by external and internal validations. The reliability of the novel correlation is compared with the complex 3D-QSAR method CoMSIA based on donor hydrogen bond, electrostatic interactions, steric occupancy, local hydrophobicity, and acceptor hydrogen bond fields. The values of correlation coefficient (R2), and root mean squared error (RMSE) for 138/34 data of training/test sets, where the predicted results of complex CoMSIA calculations were available, are 0.9173/0.6010 (R2), and 0.2503/0.4911 (RMSE) as well as 0.8753/0.3888 (R2), and 0.3287/0.6358 (RMSE) for the new and CoMSIA models, respectively. Further statistical parameters also confirm high reliability, precision, accuracy, and the goodness-of-fit of the simple model.

A novel model for prediction of stability constants of the thiosemicarbazone ligands with different types of toxic heavy metal ions using structural parameters and multivariate linear regression method.

A novel model is presented for reliable estimation of the stability constants of the thiosemicarbazone ligands with different types of toxic heavy metal ions (log ß11) in an aqueous solution, which has wide usage in environmental safety and ecotoxicology applications. The biggest reported data of log ß11 for 120 metalthiosemicarbazone complexes are used for deriving and testing the novel model. In contrast to available methods where they need the two-dimensional (2D) and three-dimensional (3D) complex molecular descriptors as well as expert users and computer codes, the novel correlation uses four additive and two non-additive structural parameters of thiosemicarbazone ligands. The calculated results of the novel correlation are compared with the outputs of the genetic algorithm with multivariate linear regression method (GA-MLR) as one of the best existing methods, which requires seven complex descriptors. The estimated results for 78 of training as well as 42 of two different test sets were established by external and internal validations. The values of statistical parameters comprising average deviation, average absolute deviation, average absolute relative deviation, absolute maximum deviation, and the coefficient of determination for 73 data of training set of New model/GA-MLR are 0.04/ - 0.25, 1.06/1.31, 14.4/18.7, 3.18/7.92, and 0.830/0.652, respectively. Thus, the predicted results of the new model are worthy as compared to the complex GA-MLR model. Moreover, assessments of various statistical parameters confirm that the new model provides great reliability, goodness-of-fit, accuracy, and precision.

A simple method for assessing chemical toxicity of ionic liquids on Vibrio fischeri through the structure of cations with specific anions.

Both water and non-water soluble ionic liquids (ILs) may be toxic where ILs soluble in water can be released into aquatic ecosystems. Toxicity of ILs can be determined as effective nominal concentration EC50 because it is important to assess the toxicity of ILs by an inhibition assay, which can evaluate the toxicological danger of ILs. A novel model is introduced for desk calculations of chemical toxicity of ILs based on Vibrio fischeri with more reliance on their answers as one could attach to the more complex outputs. It requires only specific elemental compositions of cations and anions as well as the presence of some molecular fragments in cations with particular anions. The measured values of logEC50(/µM) for 187 ILs corresponding to 250 experimental data were used to derive and test of the new model. For 153 ILs (203 datapoints), where the reported values of logEC50(/µM) as training and test sets by one of the best quantitative structure-activity relationship (QSAR) were available, the new method gives more reliable predictions. The present simple method is also tested with further 34 (47 datapoints), which confirm good forecasting reliability of the new model.

Application of laser-induced breakdown spectroscopy to assess palladium catalyst deactivation.

This work introduces a new method for the investigation of palladium (Pd) catalyst deactivation by laser-induced breakdown spectroscopy (LIBS). For this purpose, deactivation of Pd/(OH)2/C catalyst for synthesis of hexanitrohexaazaisowurtzitane (HNIW or CL-20) as a high-performance energetic compound was studied. The LIBS spectrum of fresh catalyst (Pd/(OH)2/C) with 10% Pd was compared to spent catalyst (Pd/C) containing 7% Pd. LIBS tests were also carried out under argon (Ar) ambient gas in order to correlate with the same tests under air atmosphere. Experimental results indicate that line intensities of Pd were lower for all of the spent catalyst samples under the same conditions. The C2 swan bands are also greater in spent catalyst because of deactivation, which provides a lower amount of Pd in active sites of carbon. Furthermore, the intensity of Hα in spent catalyst is lower than fresh catalyst because of conversion of Pd(OH)2/C to Pd/C during deactivation.

Energetic materials identification by laser-induced breakdown spectroscopy combined with artificial neural network.

In this study, for the first time to the best of our knowledge, a combination of the laser-induced breakdown spectroscopy (LIBS) technique and artificial neural network (ANN) analysis has been implemented for the identification of energetic materials, including TNT, RDX, black powder, and propellant. Also, aluminum, copper, inconel, and graphite have been used for more accurate investigation and comparison. After the LIBS test and spectrum acquisition on all samples in both air and argon ambient, optimized neural networks were designed by LIBS data. Based on input data, three ANN algorithms are proposed: the first is fed with the whole LIBS spectra in air (ANN1) and the second with the principle component analysis (PCA) scores of each spectrum in air (ANN2) and the other with the PCA scores of the spectrum in Ar (ANN3). According to the results, error of the network is very low in ANN2 and 3 and the best identification and discrimination was obtained by ANN3. After these, in order to validate and for more investigation of this combined method, we also used Al/RDX standard samples for analysis.

Relationship between the results of laser-induced breakdown spectroscopy and dynamical mechanical analysis in composite solid propellants during their aging.

Laser-induced breakdown spectroscopy (LIBS) has been used to analyze thermal aging in AP/HTPB composite solid propellants, where AP and HTPB are ammonium perchlorate and hydroxyl-terminated polybutadiene, respectively. The method of accelerated aging was used to obtain samples of different ages. Dynamical mechanical analysis results have been provided in order to validate the LIBS results. Many methods have been used for the accurate investigation of spectra. First, molecular bands, such as CN, C2, and AlO, were compared in different samples so that their intensity ratios could be considered. In order to discriminate more accurately between different sample spectra, principle component analysis (PCA) was used as a suitable chemometric method. All these results represent changes in the chemical structure due to increasing time and temperature.

Approach for determination of detonation performance and aluminum percentage of aluminized-based explosives by laser-induced breakdown spectroscopy.

Energetic materials containing aluminum powder are hazardous compounds, which have wide applications as propellants, explosives, and pyrotechnics. This work introduces a new method on the basis of the laser-induced breakdown spectroscopy technique in air and argon atmospheres to investigate determination of aluminum content and detonation performance of 1,3,5-trinitro-1,3,5-triazine (RDX)-based aluminized explosives. Plasma emission of aluminized RDX explosives are recorded where atomic lines of Al, C, H, N, and O, as well as molecular bands of AlO and CN are identified. The formation mechanism of AlO and CN molecular bands is affected by the aluminum percentage and oxygen content present in the composition and plasma. Relative intensity of the Al/O is used to determine detonation velocity and pressure of the RDX/Al samples. The released energy in the laser-induced plasma of aluminized RDX composition is related to the heat of explosion and percentage of aluminum.

Stereochemistry and spectroscopic analysis of bis-Betti base derivatives of 2,3-dihydroxynaphthalene.

Density functional theory (DFT) was used to study the stereochemistry, thermodynamic stability, and spectra of recently synthesized bis-Betti base derivatives of 2,3-dihydroxynaphthalene obtained through multicomponent reactions of 2,3-dihydroxynaphthalene with aminoisoxazole and benzaldehyde derivatives. The stereochemistry of the products was investigated by theoretically calculating the infrared (IR) and proton nuclear magnetic resonance ((1)H NMR) spectra of the diastereomers and comparing them to the corresponding experimental data. The thermochemical properties of the reactions, including the enthalpy, internal energy, entropy, and Gibbs free energy, were also calculated. The diastereoselectivity of the reactions was estimated from the equilibrium distribution of diastereomers. According to the results, the synthesis of bis-Betti bases is exothermic and accompanied by a decrease in entropy. The energy difference between the diastereomers is quite small, but the Gibbs free energy change for the equilibrium syn <−> anti favors the anti over syn configuration. These results are in good agreement with experimental observations.

Accurate prediction of the toxicity of benzoic acid compounds in mice via oral without using any computer codes.

Most of benzoic acid derivatives are toxic, which may cause serious public health and environmental problems. Two novel simple and reliable models are introduced for desk calculations of the toxicity of benzoic acid compounds in mice via oral LD(50) with more reliance on their answers as one could attach to the more complex outputs. They require only elemental composition and molecular fragments without using any computer codes. The first model is based on only the number of carbon and hydrogen atoms, which can be improved by several molecular fragments in the second model. For 57 benzoic compounds, where the computed results of quantitative structure-toxicity relationship (QSTR) were recently reported, the predicted results of two simple models of present method are more reliable than QSTR computations. The present simple method is also tested with further 324 benzoic acid compounds including complex molecular structures, which confirm good forecasting ability of the second model.

Simple method for reliable predicting flash points of unsaturated hydrocarbons.

This work introduces a simple method for prediction of the flash point of different classes of unsaturated hydrocarbons including alkenes, alkynes and aromatics. Elemental composition is used as a core function that can be revised for some compounds by a correcting function. The predicted flash points for a data set of 173 unsaturated hydrocarbons are in good agreement with the measured values such that the root mean square (rms) error is 9 K. The estimated flash points for 76 furthers compounds have been compared with two new group additivity methods, where these methods can be applied, that the new method gives a lower rms value. It is shown that the new model can easily be used for any unsaturated hydrocarbons with complex molecular structures.

Prediction of the condensed phase heat of formation of energetic compounds.

A new reliable simple model is presented for estimating the condensed phase heat of formation of important classes of energetic compounds including polynitro arene, polynitro heteroarene, acyclic and cyclic nitramine, nitrate ester and nitroaliphatic compounds. For CHNO energetic compounds, elemental compositions as well as increasing and decreasing energy content parameters are used in the new method. The novel correlation is tested for 192 organic compounds containing complex molecular structures with at least one nitro, nitramine or nitrate energetic functional groups. This work improves the predictive ability of previous empirical correlations for a wide range of energetic compounds. For those energetic compounds where group additivity method can be applied and outputs of quantum mechanical computations were available, it is shown that the root mean square (rms) deviation of the new method is lower.

A new method for predicting the heats of combustion of polynitro arene, polynitro heteroarene, acyclic and cyclic nitramine, nitrate ester and nitroaliphatic compounds.

A new method is presented for estimating the gross and net heats of combustion of important classes of energetic compounds including polynitro arene, polynitro heteroarene, acyclic and cyclic nitramine, nitrate ester and nitroaliphatic compounds. Elemental compositions as well as the presence of some specific polar groups and molecular fragments are important parameters in the new model. The novel method can be easily used for any complex organic compounds with at least one nitro, nitramine or nitrate functional groups by which the predictions of their heats of combustion by the available methods are inaccurate or difficult. The predicted results show that this method gives reliable predictions of heats of combustion with respect to group additivity method and computed values based on atom-type electrotopological state indices for several energetic compounds where the models can be applied.

A new approach to predict the strength of high energy materials.

This paper presents a new approach to predict the strength of energetic compounds in which there are important classes of high explosives including nitroaromatics, acyclic and cyclic nitramines, nitrate esters and nitroaliphatics. For C(a)H(b)N(c)O(d) compounds, the ratio of carbon to oxygen atoms and the predicted heat of detonation on the basis of the H(2)O-CO(2) arbitrary have been used to calculate the strength of an explosive. The new model can give good predictions for mentioned energetic compounds as determined by the Trauzl test. The novel correlation will be useful in predicting the strength or power of a new energetic compound that has significant potential in the field of explosives and propellants.

Using molecular structure for reliable predicting enthalpy of melting of nitroaromatic energetic compounds.

In this work, a reliable simple method has been introduced for predicting enthalpy of melting of nitroaromatic energetic compounds through their molecular structures. This method can be used for a wide range of nitroaromatics including halogenated nitroaromatic compounds. The contribution of hydrogen bonding and polar groups as well as structural parameters can be used to improve the predicted values on the basis of the number of carbon, nitrogen and oxygen atoms. The predicted results show that this method gives reliable prediction of standard enthalpy of melting with respect to the best available methods for different nitroaromatic compounds including high explosives with complex molecular structures.

Improved prediction of heats of sublimation of energetic compounds using their molecular structure.

A simple method is used to predict heats of sublimation of energetic compounds, which include nitroaromatics, nitramines, nitroaliphatics and nitrate esters. Molecular weight, some specific functional groups and structural parameters are fundamental factors in the new model. The root-mean-square deviation (rms) from experiment has been calculated for the predicted results of 92 different compounds. The calculated results for 15 compounds are also compared with complicated quantum mechanical computations, where computed outputs were available. The rms deviations of new correlation and reported quantum mechanical method are 9.9 and 13.8 kJ/mol, respectively. The present method improves earlier efforts of previous models through its application for important classes of energetic compounds, which contain the energetic bonds Ar-NO(2), N-NO(2), C-NO(2) and C-O-NO(2).

A new computer code to evaluate detonation performance of high explosives and their thermochemical properties, part I.

In this paper a new simple user-friendly computer code, in Visual Basic, has been introduced to evaluate detonation performance of high explosives and their thermochemical properties. The code is based on recently developed methods to obtain thermochemical and performance parameters of energetic materials, which can complement the computer outputs of the other thermodynamic chemical equilibrium codes. It can predict various important properties of high explosive including velocity of detonation, detonation pressure, heat of detonation, detonation temperature, Gurney velocity, adiabatic exponent and specific impulse of high explosives. It can also predict detonation performance of aluminized explosives that can have non-ideal behaviors. This code has been validated with well-known and standard explosives and compared the predicted results, where the predictions of desired properties were possible, with outputs of some computer codes. A large amount of data for detonation performance on different classes of explosives from C-NO(2), O-NO(2) and N-NO(2) energetic groups have also been generated and compared with well-known complex code BKW.

New method for predicting melting points of polynitro arene and polynitro heteroarene compounds.

This work introduces a new method for prediction of melting points of nitroaromatic compounds, including polynitro arenes and polynitro heteroarenes, through their molecular structures. The new model extends earlier work, which was used for carbocyclic nitroaromatic compounds, to estimate melting points of heterocyclic aromatic compounds. Some specific functional groups and structural parameters can be used to improve the predicted values on the basis of the number of carbon, hydrogen and nitrogen atoms. The predicted results show that this method gives reliable prediction of melting points with respect to previous work and well-developed group additivity methods for different nitroaromatic explosives with complex molecular structures.