Artificial intelligence–based models for the qualitative and quantitative prediction of a phytochemical compound using HPLC method

Isoquercitrin is a flavonoid chemical compound that can be extracted from different plant species such as Mangifera indica (mango), Rheum nobile , Annona squamosal , Camellia sinensis (tea), and coriander ( Coriandrum sativum L.). It possesses various biological activities such as the prevention of thromboembolism and has anticancer, antiinflammatory, and antifatigue activities. Therefore, there is a critical need to elucidate and predict the qualitative and quantitative properties of this phytochemical compound using the high performance liquid chromatography (HPLC) technique. In this paper, three different nonlinear models including artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS), and support vector machine (SVM),in addition to a classical linear model [multilinear regression analysis (MLR)], were used for the prediction of the retention time (tR) and peak area (PA) for isoquercitrin using HPLC. The simulation uses concentration of the standard, composition of the mobile phases (MP-A and MP-B), and pH as the corresponding input variables. The performance efficiency of the models was evaluated using relative mean square error (RMSE), mean square error (MSE), determination coefficient (DC), and correlation coefficient (CC). The obtained results demonstrated that all four models are capable of predicting the qualitative and quantitative properties of the bioactive compound. A predictive comparison of the models showed that M3 had the highest prediction accuracy among the three models. Further evaluation of the results showed that ANFIS–M3 outperformed the other models and serves as the best model for the prediction of PA. On the other hand, ANN–M3proved its merit and emerged as the best model for tR simulation. The overall predictive accuracy of the best models showed them to be reliable tools for both qualitative and quantitative determination.     

Isotope effects—III: Hydrogen isotope effects on conformational equilibria derivatives of cyclohexane

Conformational equilibrium isotope effects (in J mol^?1) have been measured for deuteriation of one methyl or methylene group in the trans stereoisomers of 1,3-dimethylcyclohexane (?46 ±10), 2,6- (?80 ±28) and 3,5-dimethylcyclohexanone (?40 ±15), and 3-methyl- (48 ±3) and 3-hydroxymethyl 1-trifluoromethylcyclohexane (45—49 ± 3 in toluene, acetone or methanol). The observed effects are independent of solvent for the hydroxymethyl group The isotope effects for the methyl group in trans-4 are proportional to the number of deuterium atoms.     

Handling errors as they arise in whole-class interactions

There has been a long history of research into errors and their role in the teaching and learning of mathematics. This research has led to a change to pedagogical recommendations from avoiding errors to explicitly using them in lessons. In this study, 22 mathematics lessons were video-recorded and transcribed. A conversation analytic (CA) approach was then taken to examine how mathematical errors are treated by teachers and students when they arise in interaction. Despite pedagogical recommendations, in these interactions, errors continue to be predominantly treated as something to avoid. There is a tension between the affective aspects of managing errors in interactions and the cognitive aspects. Close examination of classroom interactions enable us to see how these tensions are managed both by teachers and students.     

Comprehensive study of the effect of composition on the flame-retardant activity of antimony oxide and halogenated hydrocarbons in thermoplastic polymers

Flame retardance has been studied in the systems (a) antimony (III) oxide and decabromobiphenyl in acrylonitrile-butadiene-styrene terpolymer (ABS) and (b) antimony (III) oxide and chlorinated paraffin in high-density polyethylene (HDPE). Values of limiting oxygen index for over 70 compositions in each system have been measured and fitted by fourth-order polynomials. The triangular plots of these polynomials show complexities of the systems which cannot be revealed by traditional methods. Optimum atomic ratios for this synergistic system were found to be higher than the commonly accepted value of 3: Br/Sb = 9 and Cl/Sb = 6–7. ABS was found to be more amenable to flame retardance than HDPE; possible reasons are discussed.     

Conformational equilibria in N-chloropiperidines

Nitrogen inversion equilibria in the anancomeric piperidines 3–6, 8 and 9 have been studied by variable temperature ¹H NMR in order to determine free energy differences ΔG_e→a⁰ for one class of N-substituted piperidines by an unequivocal method, i.e. direct integration of separate NMR signals for conformers whose interconversion is slow on the NMR timescale at an easily accessible temperature. Using 6 as a model ΔG_e→a⁰ (N-chloropiperidine) has been found to be 5·3±0·1 kJ mol^-1 at 193 K; similarly a study of 10 leads to ΔG_e→a⁰ (N-chloromorpholine) = 4·2±0·1 kJ mol^-1 at 203 K.     

New upper limit on the total neutrino mass from the 2 degree field galaxy redshift survey

We constrain f(nu) identical with Omega(nu)/Omega(m), the fractional contribution of neutrinos to the total mass density in the Universe, by comparing the power spectrum of fluctuations derived from the 2 Degree Field Galaxy Redshift Survey with power spectra for models with four components: baryons, cold dark matter, massive neutrinos, and a cosmological constant. Adding constraints from independent cosmological probes we find f(nu)<0.13 (at 95% confidence) for a prior of 0.1相似文献   

Development and validation of a multiresidue method for determination of 82 pesticides in water using GC

Several methods used for the multiresidue analysis of pesticides from the environment and drinking water have been reported. However, most of these reports dealt with a small number of targeted pesticides or some special groups. A method that is simple, faster, and more cost‐effective than the environmental protection agency (EPA) method has been developed for the analysis of 82 frequently used pesticides in water samples obtained from Yeongsan and Sumjin rivers, as well as rice fields located in various locations around the two rivers. The samples were extracted by dichloromethane, and the pesticides were analyzed using a GC‐electron capture detector (ECD), followed by confirmation with GC‐MS. Recoveries were found to be between 82 and 120.1% for most of the tested pesticides, which were in agreement with the standard values dictated by the EPA. The method was potentially applied to 66 water samples for human consumption and 90 water samples from the rice fields and irrigation ditches that were collected from June to September 2007. Oxadiazon, butachlor, and alachlor were detected in some of the river water samples collected in June, iprobenfos (IBP) was detected in samples collected in August, and no pesticide was detected in September. On the other hand, chlorpyrifos‐methyl, IBP, hexaconazole, diazinon, oxadiazon, butachlor, and isoprothiolane were detected at relatively high concentrations in 48 rice paddy field water samples collected between June and September 2007. Alachlor in one sample and procymidone in some of the rice paddy field water samples were also detected in trace amounts. The results were consistent with the temporal pattern of pesticide application in Korean rice fields.     

Conformational effects in compounds with 6-membered rings—XI : Study of a conformational equilibrium in the gas phase and in solvents ranging from non-polar to water: 4-methoxycyclohexanone

The conformation free energy difference (ΔG°(1E → 1A)) for -4methoxycyclohexanone (1) has been determined in 34 solvents, ranging in polarity from tetramethylsilile to trifluoracetic acid, using weighted average vicinal coupling constants and two pairs of anancomeric model compounds (2–5). The free energy difference in the gas phase has been estimated from the equilibrium in silicone oil (DC 550), itself derived by extrapolation from data for mixtures with hexamethyldisiloxane, together with the differential solvation energies from gas phase to silicone oil extrapolated from the solvation energies of 2–5 obtained from GLC retention data.Calculations based on Abraham's reaction field theory of solvent effects on conformational equilibria correlate quite well with the general trend in ΔG°(1E → 1A) in “normal” solvents but fail to account even qualitatively for the difference in ΔG°(1E → 1A) between the gas phase and non-polar solvents.     

The lowest excited singlet states of 1-arylbutadienes: photochemical implications

PPP calculations on 1-arylbutadienes predict a forbidden transition slightly below the first allowed transition. The two lowest excited singlet states have different calculated charge densities, implying different types of photochemical reaction.     

Synthesis and spectroscopic properties of (N/O) mono- and dispirocyclotriphosphazene derivatives with benzyl pendant arms: study of biological activity

The Cl replacement reactions of hexachlorocyclotriphosphazene (trimer; N ₃ P ₃ Cl ₆ ) with sodium (N-benzyl)- aminopropanoxides (1 and 2) produced monospiro- (3 and 4), cis-, and trans-dispirocyclotriphosphazenes (13–16). The monospiro tetrakis-aminocyclotriphosphazenes (5–12) were obtained by the Cl substitutions of 3 and 4 with different secondary amines. The cis- (13 and 14) and trans-dispirophosphazenes (15 and 16) possessed 2 chiral P centers, and they were able to present meso and racemic forms, respectively. Moreover, the structures of compounds 5 and 14 were designated using X-ray data. The absolute configuration of compound 14 was found as SR in the solid state. Analytical and spectroscopic data of the phosphazenes were consistent with their suggested structures. Antimicrobial activities of the benzyl-pendant-armed cyclotriphosphazenes were scrutinized against G(+) and G(−) bacteria and yeast strains. The bacterium most affected by the synthesized compounds was Pseudomonas aeruginosa . Minimum inhibitory concentrations and minimal bacterial concentrations were in the range of 125–500 μM. Interactions between the phosphazenes (3–12 and 15) and plasmid DNA were studied with agarose gel electrophoresis. The phosphazene- DNA interaction studies of the cyclotriphosphazenes revealed that phosphazenes 3, 4, and 15 had a substantial effect on supercoiled DNA by cleavage of the double helix.