Search Results (48)

Accurate estimations of reference evapotranspiration (ETo) are critical for hydrologic studies, efficient crop irrigation, water resources management and sustainable development. The evaluation of an empirical method was carried out to estimate hourly ETo, utilizing short-wave radiation and relative humidity as a surrogate of vapor pressure deficit (VPD), calibrated under semi-arid conditions and validated for different climatic regimes (hyper-arid, arid, subhumid) using American Society of Civil Engineers Penman–Monteith (ASCE PM) (2005) values as a standard, for the state of California. For hyper-arid climatic conditions, the empirical method resulted in underestimation and had coefficient of determination (R²) values of 0.88–0.95 and root mean square error (RMSE) values of 0.062–0.115 mm h⁻¹. Hyper-arid climatic conditions correspond to lower R² and different relations between the vapor pressure deficit (VPD) and the relative humidity function (1/lnRH) that the empirical method utilizes. For the other climatic regimes (arid, semi-arid, subhumid), the empirical method performed satisfactorily. The RMSE was calculated for groups of empirical estimates corresponding to various wind velocity values, and it was satisfactory for >99% of wind speed values (u₂). The RMSE was also calculated for grouped values of the estimates of the empirical method corresponding to observed VPDs and was satisfactory for >97% of all observed values of VPD, except for hyper-arid stations (59% of u₂ and 60% of all observed values of VPD). Full article

An environmentally friendly and highly sensitive analytical method for the determination of the dye Eosin Y (EY) was developed utilizing vortex-assisted liquid–liquid microextraction based on deep eutectic solvents (DESs), combined with fluorescence detection (LPME-FLD). The extraction efficiencies of conventional solvents and various DES systems, composed of tetrabutylammonium bromide (TBAB) and alcohols (hexanol, octanol, and decanol) in different ratios, were systematically compared. DFT calculations provided insights into the most stable forms of EY in solvents of varying polarity. Theoretical Hansen solubility parameters and the COSMO-RS solvation model were applied to assess extraction efficiency. Hansen parameters were obtained via semiempirical PM7 calculations, while BP86/def2-TZVPD DFT computations were employed within the openCOSMO-RS framework. The developed method exhibited a linear calibration range between 0.1 and 130 µg·L⁻¹, with a high correlation coefficient (R² = 0.9982). The limit of detection (LOD) was established at 0.028 µg·L⁻¹. Method precision and repeatability were confirmed over two days, with relative standard deviations (RSDs) ranging from 1.1% to 2.7% and with recoveries between 99.0% and 106.2%. The proposed analytical approach was successfully applied to the determination of EY in real water samples, demonstrating both its practical applicability and alignment with green chemistry principles. Full article

Imidazolium-based ionic liquids (ILs) have been regarded as green solvents owing to their unique properties. Among these, the melting point is key to their excellent performance in applications such as catalysis, biomass processing, and energy storage, where stability and operational temperature range are critical. The utilization of neural networks for forecasting the melting point is highly significant. Nevertheless, the excessive selection of descriptors obtained by density functional theory (DFT) calculations always leads to huge computational costs. Herein, this study strategically selected only 12 kinds of quantum chemical descriptors by employing a much more efficient semi-empirical method (PM7) to reduce computational costs. Four principles of data pre-processing were proposed, and the innovative use of a simulated annealing algorithm to search for the lowest energy molecular conformation improved accuracy. Based on these descriptors, a multi-layer perceptron neural network model was constructed to efficiently predict the melting points of 280 imidazolium-based ILs. The R² value of the current model reached 0.75, and the mean absolute error reached 25.03 K, indicating that this study achieved high accuracy with very little computational cost. This study reveals a strong correlation between descriptors and melting points. Additionally, the model accurately predicts unknown melting points of imidazolium-based ILs, achieving good results efficiently. Full article

Alkaloids are naturally occurring metabolites with a wide variety of pharmacological activities and applications in science, particularly in medicinal chemistry as anti-inflammatory drugs. Because they can be labelled as active or inactive compounds against the inflammatory biological response, the aim of this work was to calibrate quantitative structure-activity relationships (QSARs) using machine learning classifiers to predict anti-inflammatory activity based on the molecular structures of alkaloids. A dataset of 100 alkaloids (58 active and 42 inactive) was retrieved from two systematic reviews. Molecules were properly curated, and the molecular geometries of the compounds were optimized using the semi-empirical method (PM3) to calculate molecular descriptors, binary fingerprints (extended-connectivity fingerprints and path fingerprints) and MACCS (Molecular ACCess System) structural keys. Then, we calibrated the QSAR models using well-known linear and non-linear machine learning classifiers, i.e., partial least squares discriminant analysis (PLSDA), random forests (RF), adaptive boosting (AdaBoost), k-nearest neighbors (kNN), N-nearest neighbors (N3) and binned nearest neighbors (BNN). For validation purposes, the dataset was randomly split into a training set and a test set in a 70:30 ratio. When using molecular descriptors, genetic algorithms-variable subset selection (GAs-VSS) was used for supervised feature selection. During the calibration of the models, a five-fold Venetian blinds cross-validation was used to optimize the classifier parameters and to control the presence of overfitting. The performance of the models was quantified by means of the non-error rate (NER) statistical parameter. Full article

A new green and highly sensitive method for the determination of rhodamine B (RhB) by deep eutectic solvent-based vortex-assisted liquid–liquid microextraction with fluorescence detection (DES-VALLME-FLD) was developed. The extraction efficiency of conventional solvents and different deep eutectic solvent (DES) systems composed of tetrabutylammonium bromide (TBAB) and an alcohol (hexanol, octanol, or decanol) in different ratios were compared. DFT calculations of intermolecular electrostatic and non-covalent interactions of the most stable RhB forms with DES and water explain the experimental DESs’ extraction efficiency. Semiempirical PM7 computations were used to obtain Hansen solubility parameters, which supported the good solubility of the monocationic RhB form in selected DESs. The dependence of the linear calibration of microextraction into 100 µL DES was observed in the RhB calibration range from 0.2 to 10.0 µg L⁻¹ with a correlation coefficient of R² = 0.9991. The LOD value was calculated to be 0.023 µg L⁻¹. The accuracy and precision of the proposed method were verified over two days with RSD values of 2.9 to 4.1% and recovery of 94.6 to 103.7%. The developed method was applied to the determination of RhB in real samples (tap water, energy drink, and lipstick). Full article

The rise of straintronics—the possibility of fine-tuning the electronic properties of nanosystems by applying strain to them—has enhanced the interest in characterizing the mechanical properties of these systems when they are subjected to tensile (or compressive), shear and torsion strains. Four parameters are customarily used to describe the mechanical behavior of a macroscopic solid within the elastic regime: Young’s and shear moduli, the torsion constant and Poisson’s ratio. There are some relations among these quantities valid for elastic continuous isotropic systems that are being used for 2D nanocrystals without taking into account the non-continuous anisotropic nature of these systems. We present in this work computational results on the mechanical properties of six small quasi-square (aspect ratio between 0.9 and 1.1) graphene nanocrystals using the PM7 semiempirical method. We use the results obtained to test the validity of two relations derived for macroscopic homogeneous isotropic systems and sometimes applied to 2D systems. We show they are not suitable for these nanostructures and pinpoint the origin of some discrepancies in the elastic properties and effective thicknesses reported in the literature. In an attempt to recover one of these formulas, we introduce an effective torsional thickness for graphene analogous to the effective bending thickness found in the literature. Our results could be useful for fitting interatomic potentials in molecular mechanics or molecular dynamics models for finite carbon nanostructures, especially near their edges and for twisted systems. Full article

This work is devoted to the study of nanosized polymer polyvinylidene fluoride (PVDF) thin ferroelectric films (two-dimensional ferroelectrics) and their composites with graphene layers, using molecular dynamics methods to (1) study and calculate the polarization switching time depending on the electric field and film thickness, (2) study and calculate the polarization switching time depending on changes of the PVDF in PVDF-TrFE film, and (3) study the polarization switching time in PVDF under the influence of graphene layers. All calculations at each MD run step were carried out using the semi-empirical quantum method PM3. A comparison and analysis of the results of these calculations and the kinetics of polarization switching within the framework of the Landau–Ginzburg–Devonshire theory for homogeneous switching in ferroelectric polymer films is carried out. The study of the composite heterostructures of the “graphene-PVDF” type, and calculations of their polarization switching times, are presented. It is shown that replacing PVDF with PVDF-TrFE significantly changes the polarization switching times in these thin polymer films, and that introducing various graphene layers into the PVDF layered structure leads to both an increase and a decrease in the polarization switching time. It is shown that everything here depends on the position and displacement of the coercive field depending on the damping parameters of the system. These phenomena are very important for various ferroelectric coatings. Full article

The study evaluated nine empirical methods for estimating reference evapotranspiration (ET_o) in Bosnia and Herzegovina (BiH) across different climatic zones. The methods compared were the Hargreaves–Samani method (HS), the modified Hargreaves–Samani method (HM), the calibrated Hargreaves–Samani method (HC), the Priestley–Taylor method (PT), the Copais method (COP), the Makkink method (MAK), the Penman–Monteith method based on air temperature and overall average windspeed (PMT₂), the Penman–Monteith method based on air temperature and regional average windspeed (PMT_1.3), and the Penman–Monteith method based on air temperature and site-specific windspeed (PMT_lok). These methods were tested against the “Food Agricultural Organization-Penman Monteith approach” (FAO-PM). The evaluation was performed using data from 20 meteorological stations in BiH, considering a common irrigation season (April–October) for two periods (2000–2005 and 2018–2022). The stations represented three climatic zones: semi-arid (SA), dry sub-humid (DSH), and moist sub-humid (MSH). The performance and ranking of the ET_o methods were analyzed using the TOPSIS method. The trend of ET_o during the common irrigation season for the period from 2018 to 2022 was determined using the Mann–Kendall test. The results of the study indicated that the HC method showed the best performance across all three climatic zones. The average root mean square error (RMSE) was 0.67 mm day⁻¹, 0.49 mm day⁻¹, and 0.50 mm day⁻¹ for the SA, DSH, and MSH zones, respectively. As an alternative to the HC method, the PT method is recommended for its favorable results in both periods and in all zones. On the other hand, the HS method exhibited the highest average overestimation, particularly in the MSH zone, where ET_o values were 18% higher compared with those of the FAO-PM method. The COP method also showed high overestimation and was not recommended for use. Regarding the MAK method, it resulted in underestimation during the period from 2000 to 2005, ranging from 17% in the DSH zone to 11% in the MSH zone. However, its performance improved during the period from 2018 to 2022, for which it ranked second place in the MSH zone. Among the PMT methods, the PMTl_ok, which utilized local average windspeed, yielded the best results. Despite performing well in the neighboring country of Serbia, the HM method showed poor overall performance in BiH. The findings of this study can serve as a foundation for further research in BiH to enhance irrigation practices in response to climate changes. Full article

This paper deals with the results of quantum chemical modeling of the monoacyl-sn-glycerol 2D cluster formation at the air/water interface using a semi-empirical PM3 method. The impact of the 2 or 3 positions of the acyl substituent on the thermodynamics of the monolayer formation is assessed for surfactants with an acyl substituent C_nH_2n+1COO chain length of n = 6–17 carbon atoms. The calculation shows a significant change in the spontaneous clusterization threshold for isomeric compounds, which differs only in the position of the acyl substituent with respect to the glycerol backbone. This change is almost equal to substituent shortening by approximately two methylene fragments. At the same time, the geometric parameters of the unit cell for resulting monolayers are not affected so drastically. The 2D films in question possess an oblique or orthorhombic unit cell with parameters for 2 and 3-monoacyl-sn-glycerol monolayers, as follows: a = 4.91 Å and 4.82 Å and b = 5.00 Å and 4.92 Å, with hydrocarbon chains tilted at t = 23.0° and 23.5°. The calculated results are in accordance with existing experimental data obtained using grazing incidence X-ray diffraction measurements and the π-A isotherm technique. Full article

Two new esters of lasalocid, that are more hydrophilic, with glucose (LasGlu) and xylitol (LasX), have been synthesized, and their complexation of monovalent cations has been studied by various spectrometric and spectroscopic methods, such as ESI mass spectrometry, ¹H, ¹³C NMR and FT-IR. Analyses of the results confirmed the synthesis of new esters with good yields. In order to carry out further studies, it was necessary to purify them using “flash“ liquid chromatography. It was confirmed that the newly obtained molecules, as well as their complexes with lithium, sodium and potassium cations, were stabilized by a strong system of intramolecular hydrogen bonds. It was found that the hydroxyl groups of esters derived from xylitol and glucose were also involved in the complexation of cations. The results of the PM6 semiempirical calculations permitted determination of the heat of formation (HOF), and visualization of the structure of the new esters and their complexes with the cations studied. All computation results are in agreement with the spectroscopic data. Full article

This article reports the synthesis, characterization, geometrical optimization, and biological studies of new MBH-based organometallic compounds of medicinal significance. The ligand (MNHA) was prepared via the Morita–Baylis–Hillman (MBH) synthetic route, from aromatic aldehyde containing multiple functional groups. Metal complexes were prepared in an alkaline medium and under other suitable reaction conditions. Spectral and elemental analyses were used to identify the structural and molecular formulas of each compound. Optimized geometry was determined through density functional theory (DFT) B3LYP and 6-311++ G (d,p) basis set for the MBH adduct, whereas structures of novel complexes were optimized with the semi-empirical PM6 method. Powder XRD analysis furnished the crystal class of complexes, with Co³⁺, Cr³⁺, and Mn²⁺ being cubic, while Ni²⁺ was hexagonal, and Cu²⁺ was orthorhombic. Moreover, the ligand, along with Ni²⁺ and Co³⁺ complexes, showed profound antibacterial action against S. aureus, E. coli, B. pumilis, and S. typhi. Additionally, all of the complexes were shown to persist in the positive antioxidant potential of the ligand. Contrarily, not a single metal complex conserved the antifungal potentials of the ligand. Full article

Soot molecules are hazardous compounds threatening human health. Computational chemistry provides efficient tools for studying them. However, accurate quantum chemistry calculation is costly for the simulation of large-size soot molecules and high-throughput calculations. Semi-empirical (SE) quantum chemistry methods are optional choices for balancing computational costs. In this work, we validated the performances of several widely used SE methods in the description of soot formation. Our benchmark study focuses on, but is not limited to, the validation of the performances of SE methods on reactive and non-reactive MD trajectory calculations. We also examined the accuracy of SE methods of predicting soot precursor structures and energy profiles along intrinsic reaction coordinate(s) (IRC). Finally, we discussed the spin density predicted by SE methods. The SE methods validated include AM1, PM6, PM7, GFN2-xTB, DFTB2, with or without spin-polarization, and DFTB3. We found that the shape of MD trajectory profiles, the relative energy, and molecular structures predicted by SE methods are qualitatively correct. We suggest that SE methods can be used in massive reaction soot formation event sampling and primary reaction mechanism generation. Yet, they cannot be used to provide quantitatively accurate data, such as thermodynamic and reaction kinetics ones. Full article

The title ligand (L^”_x), methyl 2-((4-cyanophenyl)(hydroxy)methyl)acrylate was synthesized following the Morita-Baylis-Hillman reaction scheme. Spectroscopic techniques such as: UV- Visible, FT-IR, ESI-MS, and ¹H NMR helped in characterization of the L^”_x. Complexes of Cr³⁺, Co³⁺, Ni²⁺, Mn²⁺, Cu²⁺ with L^”_x were prepared and characterized by UV- Visible, FT-IR and powder-XRD. FTIR spectrum of the L^”_x generated through DFT B3LYP method and 6-311++ G (d,p) basis set was found in good agreement with experimental spectrum. Additionally, the semi-empirical PM6 method optimization helped propose the most suitable geometries of the complexes with Cr³⁺, Co³⁺ possessing octahedral, Ni²⁺ square planner, Mn²⁺ and Cu²⁺ tetrahedral geometries. Powder-XRD patterns of the complexes have revealed cubic crystal class for Cr³⁺ and Co³⁺, whereas hexagonal, orthorhombic, and monoclinic for Ni²⁺, Mn^2+, and Cu²⁺ complexes were observed, respectively. In addition, the nano-particle size was found in the range of 8.2560–4.5316 nm for complexes. Antibacterial activity against S. aureus, E. coli, B. pumilis and S. typhi confirmed a substantially high potential, as endorsed by their Molecular docking studies, of Ni²⁺ and Cu²⁺ complexes against each bacterial strain. Moreover, all compounds exhibited positive antioxidant activities, but have no antifungal potential except L^”_x. The current study demonstrates the usefulness of these novel transition metal complexes as possible potent antibacterial and antioxidant agents. Full article

Environment-friendly materials (e.g., Honey and Mint) are used as corrosion inhibitors for aluminum in hydrochloric acid (HCl) using both the density functional theory (DFT) at the B3LYP/6–31G* basis set level and semi-empirical methods (AM1, PM3, MINDO, and RM1). The aim of this study is to investigate the inhibition efficiency (%IE) in terms of their molecular structure. The quantum chemical parameters such as the highest occupied molecular orbital energy (E_HOMO), the lowest unoccupied molecular orbital energy (E_LUMO), the energy gap (ΔE), the charge on the reactive core, the hardness (η), and the total energy have all been computed. The MINDO method was used to measure the electronic energies and charge densities of the inhibitors that were used. Theoretical calculations were also carried out, with the findings correlating well with the experimental data. Gravimetry and gasometry measurements were used to investigate the effects of honey and mint on aluminum corrosion in a 1.0 M hydrochloric acid (HCl) solution. In acid solutions, honey and mint were found to be effective inhibitors of aluminum corrosion, with honey being the better option. Because of the adsorption of its components on aluminum surfaces, the inhibitory effect of the used inhibitors was addressed. The higher dipole moment of honey than that of mint caused the adsorption of honey on the aluminum surface better. The IEs measured by gravimetry and gasometry are almost identical. Full article

In recent years, graphene (CC) and hexagonal boron nitride (h-BN) have been widely used in water purification and environmental remediation because of their unique physical and chemical properties. Therefore, based on the reaction enthalpy, equilibrium structure, atomic charge, molecular, orbital and electronic spectrum provided by a semiempirical PM7 method, the adsorption of pesticides, antibiotics and microcystin-LR on graphene and hexagonal boron nitride (h-BN) nano-systems was examined. For the adsorption of diazinon, parathion, oxacillin and ciprofloxacin, the results show that as the bond length decreases and the atomic partial charge increases, the adsorption energy increases. The removal efficiency for antibiotics is higher than that for pesticides. Regarding the co-adsorption of pesticides/antibiotics and microcystin-LR on nano-systems, hydrogen bonds play a crucial role in stabilizing the whole structure. In addition, the non-covalent interaction (NCI) diagrams show the adsorption strength of the nano-systems to the pesticides/antibiotics. The energy gap and HSAB global descriptors are calculated based on the energy values of HOMO and LUMO. It is proved that the graphene nano-system has excellent electron-accepting ability, and suitable sensor materials can be designed. Full article