rss_2.0Ovidius University Annals of Chemistry FeedSciendo RSS Feed for Ovidius University Annals of Chemistryhttps://sciendo.com/journal/AUOChttps://www.sciendo.comOvidius University Annals of Chemistry 's Coverhttps://sciendo-parsed-data-feed.s3.eu-central-1.amazonaws.com/6222d9880d198124537bf4f6/cover-image.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20220627T202947Z&X-Amz-SignedHeaders=host&X-Amz-Expires=604800&X-Amz-Credential=AKIA6AP2G7AKP25APDM2%2F20220627%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Signature=07bd3a1acd703c52ec024c4c22f087da5c9e51c12602573ab3bf3635fe4913d8200300Synthesis and characterization of novel poly(α-methyl β-alanine-b-lactone)s through hydrogen-transfer and ring-opening polymerizationhttps://sciendo.com/article/10.2478/auoc-2022-0011<abstract> <title style='display:none'>Abstract</title> <p>A series of novel poly(α-methyl β-alanine-b-lactone)s were prepared by a combination of hydrogen-transfer polymerization (HTP) of methacrylamide (MAm) and anionic ring-opening polymerization (AROP) of β-propiolactone (BPL), β-butyrolactone (BBL), and δ-valerolactone (DVL). For this purpose, poly(α-methyl β-alanine) (PmBA) having a living anionic end-group for a further extension was obtained via HTP of MAm. The anionic end-group on PmBA chains were used as initiation sites for AROP of BPL, BBL, and DVL. Fourier Transform Infrared Spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance Spectroscopy (<sup>1</sup>H-NMR) confirmed the existence of both ester and α-methyl β-alanine (mBA) units in the final products. MALDI-MS analysis revealed that the poly(α-methyl β-alanine-b-lactone)s with average molar masses of several thousand g·mol<sup>−1</sup> were obtained. DSC and TGA thermograms of each copolymer showed that the copolymers comprised the mBA and the corresponding ester units.</p> </abstract>ARTICLE2022-06-19T00:00:00.000+00:00Flow behavior of Algerian crude oils from different sourceshttps://sciendo.com/article/10.2478/auoc-2022-0009<abstract> <title style='display:none'>Abstract</title> <p>A study of the flow behavior of Algerian crude oils obtained from different fields in the TFT region (Tin Fouye Tabankort/South Algeria) was conducted using the AR2000 rheometer equipped with a Couette geometry. Rheology experiments were carried out at different shear rates and temperatures to predict the transport characteristics of crude oils. The results obtained show that all crude oils studied exhibit non-Newtonian behavior at low shear rates and quasi-Newtonian behavior at high values of the shear rate gradient. The analysis of the obtained rheological data revealed that the increase in temperature had a positive effect on the flow behavior of crude oils in pipelines.</p> </abstract>ARTICLE2022-06-19T00:00:00.000+00:00Preparation and physico-chemical study of fire retardant from chicken feathers and PP/PE compositeshttps://sciendo.com/article/10.2478/auoc-2022-0010<abstract> <title style='display:none'>Abstract</title> <p>Chicken feathers were used to reinforce low density polyethylene (LDPE) and polypropylene (PP). The physico-mechanical and flame retardation properties of the composites were investigated. Properties such as tensile strength, elongation at break, flexural strength, and modulus as well as water absorbency were determined and the results obtained were analyzed. The composites were further characterized by SEM and FTIR analyses to study the surface morphology and evidence of composite formation respectively. The Young modulus of reinforced composites were greater than that of virgin samples. The fiber/Polypropylene samples were observed to have the highest value of Young modulus, with a value of 133.33 GPa, and tensile strength value of 16.93 MPa. TGA and flame retardant tests were carried out to investigate the flame propagation and thermal properties of the composites. The results showed that the mechanical properties of composites from polypropylene were better enhanced than those from the composites of polyethylene, with an overall increase in mechanical properties when compared to the virgin polymers used. From the TGA and flame retardant test, it was observed that the more the fiber load the more the formation of char layers in the samples, hence retards the flame formation and reduced prolonged burning and flame propagation.</p> </abstract>ARTICLE2022-06-19T00:00:00.000+00:00Physico-chemical and sensory quality of pasteurized apple juices extracted by blender and cold pressing juicerhttps://sciendo.com/article/10.2478/auoc-2022-0012<abstract> <title style='display:none'>Abstract</title> <p>Worldwide, one of the most consumed fruit juices is apple juice, preferred by both adults and children due to its authentic taste, but also due to its nutritional and health benefits. Apple juice contains sugars, malic acid, soluble pectin, vitamin C, phytochemicals and minerals. The production process influences the juice composition. There is a growing market for natural cloudy apple juice, even though fruit juice is mostly consumed as clear juice. The aim of this study was to obtain cloudy apple juice by using a blender and a cold pressing juicer for extraction and to evaluate their physico-chemical and sensory qualities. The apple juice samples were obtained from three different apple cultivars: “Gala”, “Braeburn” and “Golden Delicious”. After extraction, apple juice samples were pasteurized and cooled. In this study, physico-chemical analyzes (like moisture, water activity, pH, titratable acidity, total soluble solids, electrical conductivity, color parameters) were performed immediately after processing and at 7, 14, 21 days of storage at room temperature. The results showed that the investigated parameters of the apple juice samples varied differently depending on both the apple cultivar and the processing method used. Sensory analysis showed that certain types of apples can be suitable for extracting juice using a blender (“Golden Delicious”), while others such as “Gala” apples can be used to obtain juice by cold pressing.</p> </abstract>ARTICLE2022-06-19T00:00:00.000+00:00Colloidal matter separation of industrial wastewaters from Galați City area by semipermeable membraneshttps://sciendo.com/article/10.2478/auoc-2022-0008<abstract> <title style='display:none'>Abstract</title> <p>Various studies have shown that ultrafiltration membranes are successfully involved in the removal process of most organic pollutants from wastewater. In this context, the hydrodynamic characteristics of a modified cellulose ultrafiltration membrane were evaluated. This composite membrane type has been proposed for the separation of colloidal matter from industrial wastewater in Galati City area (Romania). Another purpose of this paper was also to determine the volume flows, along with the permeate and concentrate fluxes through the technical membrane taken under study. Furthermore, a comparative analysis of three samples of industrial water from Galați City area in terms of the degree of contamination was performed. Surface modification was evaluated using scanning electron microscopy. Results indicated that the industrial wastewater from the steel factory Liberty Galati was significantly more impure than the water from Cătuşa Lake, which in turn was more impure than the water from Siret River, as indicated by comparative analysis of the water samples subjected to the ultrafiltration operation through semipermeable technical membranes. It was shown that the decrease of the permeate flux at the modified cellulosic membrane was accentuated in the first moments, probably due to the clogging of the surface pores that present an uneven distribution. The results of the present study show that the cellulosic membrane used has pore diameters which correspond to the values recommended for the retention of colloidal matter.</p> </abstract>ARTICLE2022-05-17T00:00:00.000+00:00Catalytic pyrolysis of low density polyethylene and polypropylene wastes to fuel oils by N-clayhttps://sciendo.com/article/10.2478/auoc-2022-0007<abstract> <title style='display:none'>Abstract</title> <p>Dealing effectively with plastic wastes has been a major global challenge. Different methods have been previously employed to proffer solution to plastic wastes problem however, all showed their energetic, economic and environmental implications. In this research, catalytic pyrolysis of low density polyethylene and polypropylene wastes was carried out to proffer solution to the problem. The plastic materials were collected and appropriately prepared after which ultimate and proximate analysis was carried out on them. The clay was collected from Naka, Gwer West Local Government Area of Benue State, Nigeria, thereafter, referred to as N-clay and was appropriately prepared, then analyzed by a BET analyzer for the following properties: the surface area, which was found to be 85.418 m<sup>2</sup>/g, pore size 2.100 nm and pore volume of 0.042 cc/g. Also, the XRF determination of the chemical composition of the N-clay was done and the SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratio was found to be 70.81/29.19. The N-clay and the plastics were then pyrolyzed in a chemical vapor deposition (CVD) reactor in the ratio 1:3 respectively, at 500 <sup>o</sup>C with residence time of 30 min using nitrogen as purge gas. The polypropylene yielded 70.34 % liquid oil, 6.43 % char and 23.23 % gas. The liquid was analyzed for functional groups, using Raman spectrometer. Physicochemical analysis was also done on the oil and it was determined that the oil had properties consistent with commercial-grade gasoline. The low density polyethylene yielded wax, instead of liquid, char and gas. Finally, it was concluded that the N-clay was suitable as catalyst for the pyrolysis of plastics and the fuel oil obtained from polypropylene pyrolysis is comparable to gasoline fuel.</p> </abstract>ARTICLE2022-05-17T00:00:00.000+00:00Entropy generation analysis in a gasket plate heat exchanger using non-spherical shape of alumina boehmite nanoparticleshttps://sciendo.com/article/10.2478/auoc-2022-0006<abstract> <title style='display:none'>Abstract</title> <p>The analysis deals with the thermo-hydraulic performance of a Gasket Plate Heat Exchanger used for cooling vegetable oils with a water-ethylene glycol 50% and volume fractions of non-spherical nanoparticles mixture as a refrigerant. The heat exchanger has 75 plates with a chevron angle equal to 30º. The Reynolds number of the refrigerant varies from 80 to 1530. The Reynolds number of the sunflower vegetable oil is fixed and equal to 30. The non-spherical nanoparticles used for analysis are platelet, cylindrical and brick types. Graphical results are presented for global heat transfer coefficient, heat capacity ratio, heat transfer rate, outlet temperatures, thermal and viscous entropy generation rate, and Bejan thermodynamic number. The results obtained allow us to conclude that it is possible to work with low relative flow rates using non-spherical nanoparticles, emphasizing platelet nanoparticles. The entropy generations analysis shows that very high flow rates of the refrigerant dissipate much of the energy in viscous form and do not contribute to oil cooling, with a consequent increase in the heat exchanger operating costs.</p> </abstract>ARTICLE2022-05-17T00:00:00.000+00:00Molecular docking and pharmacokinetics studies of (Curcumin) potency against Ebola virushttps://sciendo.com/article/10.2478/auoc-2022-0004<abstract> <title style='display:none'>Abstract</title> <p>The Ebola virus disease causing hemorrhagic fever in human, has been known for nearly about 40 years, with the most recent outbreak being in West Africa creating humanitarian crisis, where over 11,308 deaths were recorded as reported in 30<sup>th</sup> March, 2016 (World Health Organization). Till now, Ebola virus drugs have been far from achieving regulatory FDA approval, and coupled with toxicity of these drugs, it is become imperative to appraise the available trail drugs, as well as looking into alternative natural resources of tackling menace. Therefore, <italic>in silico</italic> methods were used to assess the potency of the bioactive phytochemical, Curcumin from Turmeric and results compared with those obtained for some selected trial drugs in use for the treatment of Ebola virus. This study is focused on molecular docking of Curcumin and eight commercially available drugs (Amodiaquine, Apilimod, Azithromycin, Bepridil, Pyronaridine, Remedesivir and Tilorone) against Ebola transcription activator VP30 proteins (PDB: 2I8B, 4Z9P and 5T3T) and their ADMET profiling. The results showed that binding affinity (ΔG kJ/mol) ranged from -5.8 (Tilorone) to -7.3 (Remdesivir) for 218B, -6.4 (Tilorone) to -8.2 (Pyronaridine, Remedesivir) and -5.8 (Bepridil) to -7.4 (Pyronaridine). Curcumin could be more desirable as inhibitor for than Tilorone, Dronedarone and Bepridil in the treatment of Ebola virus; the ADMET profile revealed that Curcumin presents attractive pharmacokinetic properties than the trial drugs.</p> </abstract>ARTICLE2022-04-13T00:00:00.000+00:00Malachite green adsorption by calcium-rich crab shell char via two-stage adsorber designhttps://sciendo.com/article/10.2478/auoc-2022-0005<abstract> <title style='display:none'>Abstract</title> <p>The present work was aimed to evaluate the optimum mass of crab shell biochar and adsorption contact time in a two-stage adsorber design for malachite green. The model was developed to predict optimum adsorbent mass and adsorption profiles at specified volumes and concentrations of dye effluent. Results show that the adsorbent mass can only be reduced by 1.91 % because of the adsorbent’s strong affinity towards malachite green. Accordingly, the adsorption contact time to achieve equilibrium has dramatically reduced from 150 min to 31 min. In the performance evaluation, the adsorbent mass in stage-1 is always higher than that in stage-2 to subside the adsorbent load in achieving the target removal at optimum dosage. From the response surface methodology, the most significant parameters in two-stage adsorber design are adsorption time at stage-2 and malachite green concentration. The predicted values of adsorbent mass and time are essential in designing the cost-competitive two-stage adsorption process for industrial wastewater treatment.</p> </abstract>ARTICLE2022-04-13T00:00:00.000+00:00Synthesis and characterization of poly(ε-caprolactone) tetra-arm star polymer using tetra terminal alkynyl-substituted phthalocyanine by the combination of ring-opening polymerization and “click” chemistryhttps://sciendo.com/article/10.2478/auoc-2022-0003<abstract> <title style='display:none'>Abstract</title> <p>The synthesis of poly(ε-caprolactone) (PCL) tetra-arm star polymer was carried out using “click” chemistry and ring-opening polymerization techniques. For this purpose, poly(ε-caprolactone) azido (PCL-N<sub>3</sub>) was acquired using ring-opening polymerization of ε-caprolactone and 2-[2-(2-azidoethoxy)ethoxy]ethanol (N<sub>3</sub>ol). N<sub>3</sub>ol was obtained using sodium azide and 2-[2-(2-chloroethoxy)ethoxy]ethanol. 4-(prop-2-ynyloxy)-phthalonitrile was obtained by using 4-nitrophthalonitrile and propargyl alcohol. 2(3),9(10),16(17),23(24) Tetrakis-[(prop-2-ynyloxy)-phthalocyaninato]zinc(II) (Pc-propargyl) was synthesized by using 4-(prop-2-ynyloxy)-phthalonitrile and a metal salt. By reacting Pc-propargyl and PCL-N<sub>3</sub>, PCL tetra-arm star polymer was obtained by “click” chemistry. The products were characterized via scanning electron microscopy, <sup>1</sup>H-nuclear magnetic resonance spectroscopy, ultraviolet-visible spectrophotometry, Fourier-transform infrared spectroscopy, and gel permeation chromatography instruments. The spectroscopic analyses of PCL tetra-arm star polymer prove that the star polymer was built through the combination of ROP and “click” chemistry. We provided a protocol for PCL tetra-arm star polymer, and a statement of reproducibility with respect to the properties of this tetra-arm star polymer. This study is an example of a novel type of combination reaction, from ring-opening polymerization to “click” chemistry using phthalocyanine. This can open the door for diverse tetra-arm star polymer synthesis that could potentially cause major advances in synthetic macromolecular chemistry.</p> </abstract>ARTICLE2022-04-13T00:00:00.000+00:00Toxic metals in soil depths from selected abandoned sites: Occurrence, sources, ecological and human health riskhttps://sciendo.com/article/10.2478/auoc-2022-0002<abstract> <title style='display:none'>Abstract</title> <p>This study provides a comparative assessment of cadmium (Cd), lead (Pb), chromium (Cr), nickel (Ni), copper (Cu), manganese (Mn), zinc (Zn), and iron (Fe) pollution occurrence, sources, and exposure risk in soils from selected abandoned sites. The concentrations of metals were determined using atomic absorption spectrophotometry. The metals occurrence ranged from 0.02 (Zn) to 16600 mg kg<sup>−1</sup> (Fe) in the order of subsoil &gt; topsoil with petroleum tank farm and fuel/gas service station exhibiting high metal loading. The sources of metals are anthropogenic and geologic. The hazard index values for infants’ were higher than that of adults, and the inhalation risk for adults’ was considerably higher than for infants’ exposure. The ecological risk of Cd, Pb, Cr, Ni, and Zn falls in the contamination to pollution index. This study revealed the need for clean-up and restoration of abandoned site soils.</p> </abstract>ARTICLE2022-03-03T00:00:00.000+00:00Glycosylated stigmasterol from the rind of https://sciendo.com/article/10.2478/auoc-2022-0001<abstract> <title style='display:none'>Abstract</title> <p><italic>Napoleonaea imperialis</italic> rinds were separated from the seeds and extracted via maceration using methanol. The crude methanol extract was partitioned with <italic>n</italic>-hexane and dichloromethane to yield <italic>n</italic>-hexane fraction (11.01 g), dichloromethane fraction (35.16 g) and methanol fraction (101.75 g). Dichloromethane fraction was chromatographed and purified to give a compound whose structure was elucidated using one-dimension and two-dimension nuclear magnetic resonance (NMR) experiments. The isolated compound was characterized as glycosylated stigmasterol.</p> </abstract>ARTICLE2022-03-03T00:00:00.000+00:00Separation of waste plastic resulting from electrical products by forced aeration flotationhttps://sciendo.com/article/10.2478/auoc-2021-0015<abstract> <title style='display:none'>Abstract</title> <p>The separation of four waste plastic samples - Polyvinyl chloride (PVC), Acrylonitrile butadiene styrene (ABS), Polycarbonates (PC), and Polyamides (PA) resulting from electrical products in three bicomponent plastic mixtures (PVC-ABS, PVC – PA, and PVC - PC) was performed by using four different flotation solutions (5%, 10%, 20%, and 30% concentration) of CaCl<sub>2.</sub> Furthermore, the waste plastic samples were analyzed in terms of density, specific volume, particle size, initial water content, and water absorption capacity, while the flotation solutions were analyzed in terms of pH, density, electrical conductivity, and refractive index. Results showed that from the analyzed waste plastic samples, the PVC sample has the highest density (1.3823 g/cm<sup>3</sup>), followed by PC (1.2034 g/cm<sup>3</sup>) and PA (1.0607 g/cm<sup>3</sup>), while the ABS (0.9723 g/cm<sup>3</sup>) presented the lowest value. The highest recovery rate was obtained for the PVC samples (98.10 % - 99.75 %) when it was mixed with ABS, whereas the highest purity was measured for ABS samples (98.29 % - 99.76%) in the case of the same mixture.</p> </abstract>ARTICLE2021-08-10T00:00:00.000+00:00Mechanical and thermal behavior of plantain peel powder filled recycled polyethylene compositeshttps://sciendo.com/article/10.2478/auoc-2021-0017<abstract> <title style='display:none'>Abstract</title> <p>In the arduous search for ways to clean up the environment and produce viable materials from waste plastics; plantain peel powder filled low density polyethylene wastes (wLDPE) were developed through melt mixing and compression moulding techniques. Optimum properties were determined at 15, 55 and 30 % formulation of plantain peel powder, and <italic>Kankara</italic> clay respectively. Composition with optimum properties has tensile strength of 55.5 MPa, flexural strength of 50.45 MPa and elastic modulus of 2.30 GPa with corresponding minimal water absorption of 0.95% after 30 days immersion period at room temperature. The thermal properties investigated by Dynamic Mechanical Analysis showed that the composite has better thermal stability at higher temperature than wLDPE. Similarly, through creep analysis, the composite was observed to have better load bearing capability at elevated temperature than waste low density polyethylene material. These results indicate that incorporation of treated plantain peel powder and <italic>Kankara</italic> clay into wLDPE enhanced the mechanical, thermal and creep resistance of wLDPE. This implies load bearing capability and potential suitability for different wall tiles applications.</p> </abstract>ARTICLE2021-12-02T00:00:00.000+00:00Evaluation of drug release kinetics from polymeric nanoparticles loaded with poorly water-soluble APIshttps://sciendo.com/article/10.2478/auoc-2021-0020<abstract> <title style='display:none'>Abstract</title> <p>The aim of this research was to investigate the release behavior of a combination of two poorly water-soluble active pharmaceutical ingredients (APIs) from poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles. Amlodipine besylate - AML, a calcium channel blocker, and valsartan - VAL, an angiotensin II receptor antagonist drug, were used as poorly water-soluble model drugs. PLGA nanoparticles loaded with AML-VAL (1:16 w/w) were obtained by nanoprecipitation using an amphiphilic block copolymer - Pluronic F127 as stabilizer. The drugs release from the PLGA nanoparticles was determined by a dialysis membrane method under sink conditions. Nanoparticles provided a slow release for both APIs and an attenuated burst effect compared to free drug. Five kinetics models such as Zero-order, First-order, Korsmeyer-Peppas, Higuchi and Hixson-Crowell were applied to predict drug release profiles. The Higuchi and Korsmeyer-Peppas models (R<sup>2</sup> &gt; 0.97) best described physicochemical release phenomenon for each PLGA formulations.</p> </abstract>ARTICLE2021-12-10T00:00:00.000+00:00Evaluation of the rheological properties of the dough and the characteristics of the bread with the addition of purple potatohttps://sciendo.com/article/10.2478/auoc-2021-0019<abstract> <title style='display:none'>Abstract</title> <p>The aim of this study was to determine the rheological characteristics of the dough at the addition of purple potato powder in different quantities (0-100 g). The wheat flour types 480 and 1250 were used. The rheological characteristics of the dough were determined with the help of Chopin Alveograph analyzing the tensile strength. The rheological measurements were made with the HAAKE RheoWin Mars 40 rheometer and the dough’s viscoelastic modulus was analyzed at the frequency of 1-20 Hz. The bread samples were analyzed in terms of volume, porosity, color and texture. The textural parameters determined with the help of the texturometer were the elasticity, adhesiveness and stickiness of the bread crumb. It has been found that the addition of purple potato dough does not adversely alter the rheological properties of the dough. The elasticity and stickiness of the bread core increases with the increase of potato addition in the case of whole-grain flour. The color of the bread intensifies as the dose of purple potato powder increases.</p> </abstract>ARTICLE2021-12-10T00:00:00.000+00:00Test of inhibitors for preventing corrosion of steel reinforcement in concretehttps://sciendo.com/article/10.2478/auoc-2021-0016<abstract> <title style='display:none'>Abstract</title> <p>Concrete is more widely used than any other manmade material. The objective of this paper is to investigate the behavior of reinforced cement when migration corrosion and guar gum inhibitors are used. The concrete samples were exposed in aggressive media H<sub>2</sub>SO<sub>4</sub> 1 M and in the presence of 1∙10<sup>-3</sup> M Cl<sup>-</sup>. Electrochemical measurements such as half-cell potential, polarization resistance and Tafel extrapolation methods were performed in order to obtain information on the corrosion behavior of the reinforcing steel in cement mortar. Results demonstrate high resistance polarization and low corrosion rate for concrete sample with inhibitor. The corrosion rate decreases approximately 95% in presence of locust bean gum and 80% in presence of migration inhibitor.</p> </abstract>ARTICLE2021-09-01T00:00:00.000+00:00Determination of some phenolic acids in Algerian propolishttps://sciendo.com/article/10.2478/auoc-2021-0018<abstract> <title style='display:none'>Abstract</title> <p>Propolis is a resinous material collected by bees from various plant exudates, rich in well-known phenolic compounds, such as phenolic acids, that are important to health. Extracts of propolis are very complex matrices that are hard to test. The purpose of this study was to characterize some of the propolis phenolics that were collected from five different districts in Algeria. The High-Performance Liquid Chromatography (HPLC), a modern quantitative method, has been adopted to identify the phenolic acids. Moreover, total phenolic content of four different phenolic acids were identified, with the most abundant being chlorogenic acid, followed by caffeic acid, gallic acid, and <italic>p</italic>-coumaric acid, the obtained ratios from phenolic acids being in the range of 52.193 to 148.151 μg/g, 0.043 to 7.128 mg/g, 0.328 to 0.440 mg/g and 0.328 to 0.440 mg/g, respectively. Overall, our analysis indicates that all the samples of propolis tested are healthy sources of phenolic acids and the significant differences in the concentrations of the acids were observed for propolis samples from north and south of Algeria. It is probably the effect of different conditions of the collection of the resin and secrets by bees.</p> </abstract>ARTICLE2021-12-02T00:00:00.000+00:00Synthesis, characterization, and analysis against SARS CoV-2 of novel benzimidazolium saltshttps://sciendo.com/article/10.2478/auoc-2021-0021<abstract> <title style='display:none'>Abstract</title> <p>In acute conditions, vaccines are very important, although they provide antibodies for fighting against COVID-19 for a certain period. It is necessary to produce an anti-viral agent for a usual healing process against SARS CoV-2 which is responsible the pandemic we are living in. Many drugs with benzimidazole main scaffold are still used in a wide variety of treatment procedures. In this case, substituted benzimidazole structures could be good candidates for fighting against COVID-19. Theoretical calculation methods could be a key tool for overcome the difficulties of individual analyzing of each new structure. In this study, new benzimidazole structures were synthesized and characterized for <italic>in silico</italic> evaluation as anti-viral agent. The molecules were optimized and analyzed for reactivity with Koopmans Theorem. Also, molecular docking simulations were performed for SARS coronavirus main peptidase (PDB ID: 2GTB), COVID-19 main protease (PDB ID: 5R82), and papain-like protease of SARS CoV-2 (PDB ID: 6W9C) crystals.</p> </abstract>ARTICLE2021-12-30T00:00:00.000+00:00Heavy metal levels in spent engine oils and fingernails of auto-mechanicshttps://sciendo.com/article/10.2478/auoc-2021-0004<abstract> <title style='display:none'>Abstract</title> <p>The levels of some heavy metals in spent engine oils and in the fingernails of auto-mechanics were studied. Engine oils and fingernails were collected from auto-mechanics who had practiced between ≤ 5 years, ≤ 10 years and ≤ 15 years in 3 auto-mechanic workshop clusters. Pb, Ni, V, Cd, and As levels were determined using Atomic Absorption Spectrophotometer. The mean levels of Pb, Ni, V and Cd in spent engine oils were 14.31, 2.25, 0.38 and 2.07 ppm respectively, and these far exceeded their permissible exposure limits. The mean levels of heavy metals in the fingernails of auto-mechanics who had practiced for ≤ 5 years, ≤ 10 years and ≤ 15 years were all considerably below their pathological thresholds. Thus, auto-mechanics in the study area are exposed to unsafe levels of Pb, Ni, V, and Cd, but no immediate threat of their toxicities in the study population exist. However, a progressive bioaccumulation of the heavy metals was observed with increase in years of practice.</p> </abstract>ARTICLE2021-04-03T00:00:00.000+00:00en-us-1