Search results

The purpose of this paper is to predict the octanol/water partition coefficient (K_ow) of 43 organophosphorous compounds.

A quantitative structure-property relationship analysis was performed on a series of 43 pesticides using multiple linear regression and support vector machines methods, which correlate the octanol-water partition coefficient (K_ow) values of these chemicals to their structural descriptors. At first, the data set was randomly separated into a training set (34 chemicals) and a test set (nine chemicals) for statistical external validation.

Models with three descriptors were developed using theoretical descriptors as independent variables derived from Dragon software while applying genetic algorithm-variable subset selection procedure.

The robustness and the predictive performance of the proposed linear model were verified using both internal and external statistical validation. One influential point which reinforces the model and an outlier were highlighted.

The purpose of this paper is to predict the aquatic toxicity (LC50) of 92 substituted benzenes derivatives in Pimephales promelas.

Quantitative structure-activity relationship analysis was performed on a series of 92 substituted benzenes derivatives using multiple linear regression (MLR), artificial neural network (ANN) and support vector machines (SVM) methods, which correlate aquatic toxicity (LC50) values of these chemicals to their structural descriptors. At first, the entire data set was split according to Kennard and Stone algorithm into a training set (74 chemicals) and a test set (18 chemical) for statistical external validation.

Models with six descriptors were developed using as independent variables theoretical descriptors derived from Dragon software when applying genetic algorithm – variable subset selection procedure.

The values of Q2 and RMSE in internal validation for MLR, SVM, and ANN model were: (0.8829; 0.225), (0.8882; 0.222); (0.8980; 0.214), respectively and also for external validation were: (0.9538; 0.141); (0.947; 0.146); (0.9564; 0.146). The statistical parameters obtained for the three approaches are very similar, which confirm that our six parameters model is stable, robust and significant.

Reviews compound physico‐chemical properties and water and soil properties influencing the transport and distribution of organochlorine pesticides, polychlorinated biphenyls (PCBs) and chlorophenols in a water and soil environment. As highly hydrophobic compounds of low water solubility, organochlorine pesticides and PCBs are rapidly and strongly sorbed by most soils and sediments. The sorption of weakly acidic chlorophenols comprises both molecular and ionic forms and depends not only on the soil/sediment organic matter content but also on the pH and ionic strength of the aqueous phase. Briefly describes the analytical methods for trace analysis of organocholorine pesticides, PCBs and chlorophenols in water and soil/sediment samples. Presents some results of those micropollutants’ analysis in surface, ground and drinking waters, soils, river sediments and wet depositions in Croatia.

The purpose of this paper is to explore inhalation levels and dermal exposure to toluene among printing workers who wore no personal protective equipment; it is conducted in a plastic bag factory. Using a charcoal cloth pad (CCP) as a dermal sampler to assess skin permeation of liquid toluene is also investigated.

In total, 27 stationary air samples as well as urine and dermal samples were collected over 9 days from 11 printing workers. Six pieces of CCP were wrapped on each of the workers’ fingers for the dermal sample collection. Air samples were collected and analyzed according to NIOSH No. 1501, and 65 post-shift urine samples were collected and analyzed using gas chromatography equipped with headspace sampler (GC-HS/FID). Multiple linear regression was employed to analyze the association between the studied variables.

The mean (SD) urinary toluene (UTol) level was 13.42 (9.72) ug/L. Toluene on the CCP (TolCCP) was a meaningful predictor for UTol (p-value=0.027) with r and r² values of 0.441 and 0.195, respectively. The r and r² of the model using the toluene time-weighted average concentrations in air were 0.739 and 0.546, respectively. The absorbed dose of toluene determined from the TolCCP ranged from 1.05 to 91.94 mg, accounting for 12.3 percent of the threshold limit value (TLV).

Dermal exposure was insignificant when workers wore respirators, but when not, dermal absorption could contribute to the overall uptake and exposure above the TLV. Appropriate gloves should be assigned to the workers to reduce dermal exposure to toluene.

A laboratory experiment was conducted in the soil laboratory in the Department of Environment and Environmental Pollution, Environment and Natural Resources Research Institute, National Centre for Research. The purpose of this paper is to study the movement of crude oil through soil column.

Polyvinyl chloride columns were filled with Shambat soil, amended with three concentrations of light crude oil (0.16, 0.32, and 1.28 ppm), obtained from Petrodar Oil Company. Soil samples were taken from 5 and 10 cm depths after two, 14 and 28 days from crude oil addition. At each sampling date, the recovery of petroleum hydrocarbons measured.

The results obtained indicated that high by significant differences among the different concentrations, different depths and different sampling durations. Moreover, the downward mobility of petroleum hydrocarbons decreased with increasing crude oil concentration.

Results of the experiment revealed the importance of studying the fate and mobility of total petroleum hydrocarbons (TPH) in soils in order to facilitate a proper reclamation practice specially in oil polluted sites.

The large number and big variety of online databases in the field of environmental sciences and chemistry underlines the need for a comparative evaluation approach. In this paper 12 evaluation criteria are presented. The criteria are divided into: • general criteria: SI (size of the data‐source), CO (cost of one hour online searching), UP (update of online database), and AV (availability on other media) • chemical‐relevant criteria: NU (number of chemicals), ID (identification parameter for chemicals), CT (testset chemicals), CD (development of chemicals) • environmental‐relevant criteria: IP (information parameters for chemical substances), PD (parameter development) and • criteria describing environmental chemicals: US (use of chemical substances), QU (quality of database). A six number scoring system is applied on these criteria. Furthermore a comparative evaluation approach, the so‐called Hasse‐diagram‐technique is presented for 19 bibliographic online databases using the criteria mentioned above. In this approach maximals (‘good’ databases) and minimals (‘bad’ databases) can be identified, for example. Using the Hasse‐diagram‐technique changes in the database content from 1995 to 1998 applied on the 19 databases can be visualised.

The purpose of this paper is to predict the retention times of 84 pesticides or toxicants.

Quantitative structure – retention relationship analysis was performed on a set of 84 pesticides or toxicants using a hybrid approach genetic algorithm/multiple linear regression (GA/MLR).

A model with six descriptors was developed using as independent variables. Theoretical descriptors derived from Spartan and Dragon softwares when applying GA/MLR approach.

A six parameter linear model developed by GA/MLR, with R² of 90.54, Q² of 88.15 and S of 0.0381 in Log value. Several validation techniques, including leave-many-out cross-validation, randomization test, and validation through the test set, illustrated the reliability of the proposed model. All of the descriptors involved can be directly calculated from the molecular structure of the compounds, thus the proposed model is predictive and could be used to estimate the retention times of pesticides or toxicants.

Alzheimer’s disease (AD), the most common cause of dementia, is a neurodegenerative disorder caused by the aggregation of amyloid-beta (Aβ) at outside of neuron cells and also due to tau aggregation inside the cell. Corosolic acid is aimed to be selected as a main active constituent of Lagerstroemia speciosa for the study.

In the present study, molecular docking of corosolic acid and tau protein was examined using PyRx-v.0.8 software. Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) properties were described and a molecular dynamics study of the bound complex was performed using Desmond.

The docking score and interactions suggested that the corosolic acid (CID:6918774) could bind to tau protein to prevent the fibrillar network, to prevent AD. During simulation corosolic acid-bound protein root mean square deviation (RMSD) values showed more stability when compared to the Apo form of protein. Molecular dynamics study of tau protein and corosolic acid complex gave the insights to develop a drug-like candidate against AD.

The use of corosolic acid of Lagerstroemia speciosa to prevent AD is supported by preliminary analysis on a computational basis. This compound should explore in terms of experimental strategies for the further drug development process. However, in vitro and in vivo evaluation studies are required to suggest the use of corosolic acid against AD.

The purpose of this paper is to investigate some multiple solutions for carbon nanotubes (CNTs) in a porous channel with changing walls. Moreover, the intention of the study is to examine the physicochemical and rheological properties of titania and CNTs.

The mathematical modeling is performed for the laws of conservation of mass, momentum and energy profiles. Governing partial differential equations are transformed into ordinary differential equations by applying suitable similarity transformation and then solved numerically with the help of shooting technique.

The effects of different physical parameters on the rheology of nanofluids are discussed graphically and numerically, in order to make the analysis more interesting. The present study revealed that multiple solutions of nanofluids in a channel with changing walls are obtained only for the case of suction.

Some new branches of the solution for nanofluids in a channel with changing walls are obtained in this research, which has never been reported before. Combined effects of physicochemical and rheology of titania and carbon nanotubes are investigated briefly. The effects of physical parameters on velocity and temperature profile are examined in detail which is more realistic than real-world problem.

The objective was to outline a process for selecting hazardous substances as pollution indicators that imply a chemical risk for the recycling of wastewater residues on arable land and for wastewater discharge into receiving waters. The reviewed methodologies showed one commonality: grouping of various characteristics that symbolise hazardous properties. From each group, one or several indicator substances were selected to represent the hazardous property of that specific group. The selected set of indicator substances represented the chemical risk characteristics as a whole. One conclusion is that it is difficult to create a comprehensive list of indicator substances for the monitoring of chemical risks in wastewater and residues. Due to the insufficiency of knowledge about the chemical risks from complex systems such as a wastewater system and the methodology for selecting indicator substances, many simplifications have to be accepted. The 100,000 substances present in the technosphere, of which 30,000 are regarded as “everyday” chemicals, may end up in wastewater systems. We have a limited knowledge of many of these substances, thereby providing a weak base for assessing the true chemical risks in wastewater and residues for reuse on arable land. Although the pollution situation will not entirely be understood by measuring the status of only a few substances (important substances may be overlooked), detected substances indicate a specific pollution situation in wastewater or sludge, thus increasing our knowledge about the current concentrations.