bluuebunny/crossref_metadata_2025 huggingface dataset:
Deposition and characterization of Cu4SnS4 thin films by chemical bath deposition method
Authors: Kassim Anuar , Tee Tan Wee , Abdullah Abdul Halim , Nagalingam Saravanan , Min Ho Soon
Published: December 2019

A low cost chemical bath deposition method has been used for the preparation of Cu4SnS4 thin films onto indium tin oxide glass substrate. The deposition parameters such as bath temperature (50 °C), deposition time (120 min), electrolyte concentration (0.05 M) and bath pH (1.5) were optimized to obtain good quality thin films. The structural, surface morphological and optical properties of thin films were studied by X-ray diffraction, an atomic force microscopy and an UV-Vis Spectrophotometer, respectively. The X-ray diffraction study revealed that the Cu4SnS4 films were polycrystalline in nature with the preferential orientation along the (221) plane. The atomic force microscopy results indicated that the films were smooth, uniform and the substrate surface was covered completely at these experimental conditions. These films exhibited p-type semiconductor behavior with the band gap energy about 1.57 eV.
Fast and selective HPLC-DAD method for determination of pholcodine and related substances
Authors: Petkovska Ana , Babunovska Hristina , Stefova Marina
Published: December 2019

Quality control of pharmaceuticals requires development of fast, efficient and reliable methods for determination of active compounds as well as known and very often unknown impurities within defined concentration ranges. In this work, a simple and rapid HPLC-UV-DAD method for identification and quantification of pholcodine process related impurities and some degradation products was developed and validated. Pholcodine and its five structural analogues such as morphine, codeine, thebaine, oripavine, and papaverine were separated in less than 10 minutes using reversed phase LiChrospher C-8 column. For optimal chromatographic performance with reproducible retention times, gradient elution with 2% ammonium hydroxide in water and acetonitrile was used. The method was validated by establishing its selectivity, specifity, sensitivity, linearity, intra- and inter-day precision and robustness. All tested parameters confirmed that the method is suitable for determination of pholcodine and its five impurities in pharmaceutical drug samples. The results obtained from real sample analysis give support to the suitability of the proposed method for the purpose of quality control.
N-n-octylaniline as a new reagent for analytical liquid-liquid extraction of yttrium(III) from matrices of various metal ions
Authors: Kokare Balasaheb N. , Mandhare Aniruddha M. , Kolekar Sanjay S. , Anuse* Mansing A.
Published: December 2019

A systematic study of solvent extraction behavior of yttrium(III) with N-n-octylaniline from salicylate media was carried out. Yttrium(III) was quantitatively extracted from 0.02–0.05 mol dm–3 NaSal at pH 9.7 – 10.5 with 0.17 mol dm–3 N-n-octylaniline in xylene. The extraction was found to proceed by an anion exchange mechanism with the extraction species being [CH3(CH2)7(C6H5)NH2+Y(C7H4O3)2–] ascertained on the basis of slope analysis. The extracted metal ion was separated by selective stripping with hydrochloric acid or perchloric acid from the metal loading organic phase and estimated spectrophotometrically following a complexation with Alizarin Red S. A binary separation of yttrium(III) from Th(IV), U(VI), Zr(IV), Nb(V), La(III), Nd(III), Ce(IV) and Gd(III) is discussed.
Effect of sonication applied during production of carbon fiber/epoxy resin composites evaluated by differential scanning calorimetry and thermo-gravimetric analysis
Authors: Bogoeva-Gaceva Gordana , Dimeski Dimko , Heraković Niko
Published: December 2019

The influence of ultrasonic treatment, applied during the impregnation of carbon fiber bundle byepoxy resin system, on thermal behavior of carbon fiber/epoxy resin composites in the course of crosslinknetworkformation has been analyzed by differential scanning calorimetry (DSC). It was previouslyshown [1] that this treatment has resulted in drastically increased interlaminar shear strength (ILSS) ofthe bulk composites, produced by hot pressing. The enhanced ILSS was attributed to the formation ofmore homogeneous and dense network, as revealed by epoxy consumption rate and increased Tg. In thispaper, DSC analysis is applied to further investigate peculiarities of carbon fiber/epoxy systems, exposed toultrasonic treatment, during isothermal and non-isothermal curing and post-curing. The acceleration of thecuring reaction as a consequence of sonication effects was found for all fiber/polymer systems, regardlessthe surface chemistry of the fibers. The stronger interfacial bond in epoxy sized carbon fiber composites,favored by ultrasound treatment, has also generated differences in thermal behavior of the compositesduring their degradation followed by TGA/DTG.
Critical review of supercritical fluid extraction of selected spice plant materials
Authors: Sovilj* Milan N. , Nikolovski Branislava G. , Spasojević Momčilo Đ.
Published: December 2019

Supercritical fluid extraction (SFE) is one of the relatively new efficient separation method for the extraction of essential oils from different plant materials. The new products, extracts, can be used as a good base for the production of pharmaceutical drugs and additives in the perfume, cosmetic, and food industries. The aim of this work was to analyze the supercritical carbon dioxide extraction (SC-CO2) of oils from the selected spice plant materials. In this paper the process parameters such as pressure, temperature, solvent flow rate, size of grinding materials, and ratio of the co-solvent were presented for the selected spice plant materials: black pepper, caraway, celery, cinnamon, clove, coriander, daphne, fennel, ginger, hyssop, juniper, lavender, oregano, pennyroyal, red pepper, safflower, sage, turmeric, and vanilla. The values of operating conditions were: pressure from 7.5 to 68 MPa, temperature from 293 to 363 K, solvent flow rate from 0.003 to 30.0 kg/h, and diameter of grinding material from 0.17 to 3.90 mm. The global yield and quality of the extracts all of the plant material investigated, as well as the possibility of their application in the food, cosmetics and pharmaceutical industries were analyzed. The composition of the extracts was wery complex, and in every case the extract was composed of more than 200 components. All the compounds from the CO2 extracts were classified in the following groups: monoterpene, sesquiterpene, oxygenated monoterpene, and oxygenated sesquiterpene and other hydrocarbon groups. In some of the systems investigated the different mathematical models (Sovová, Hong), which have taken from the literature, were used to correlate the experimental data.
Use of semi-conducting bismuth sulfide as a photocatalyst for degradation of rose bengal
Authors: Sharma Shweta , Ameta Rakshit , Malkani R. K. , Ameta Suresh C.
Published: December 2019

Different methods have been adopted for the removal and degradation of dyes from effluents of textile, dyeing and printing industries. These methods have their own merits and drawbacks. In the present investigation, bismuth sulfide has been used as a photocatalyst for the degradation of rose Bengal. The effect of different parameters like the pH, concentration of dye solution, amount of semiconductor and light intensity on the rate of reaction has been investigated. The reaction follows pseudo-first order kinetics. The optimum conditions were obtained as: [rose Bengal] = 1.60·10–5 M; Bi2S3 = 0.10 g; pH = 8.5, and light intensity = 50.0 mW·cm–2. The rate constant was 4.68·10–5 sec–1. A mechanism has been proposed for the degradation of rose Bengal involving hydroxyl radicals.
Effect of benzocyclobutadieno-annelation on cyclic conjugation in perylene
Authors: Gutman* Ivan , Stojanovska Beba
Published: December 2019

Earlier studies showed that the intensity of cyclic conjugation in the central ring R of perylenecan be significantly altered by means of benzo-annelation. In particular, linear (resp. angular) benzoannelationwas found to decrease (resp. increase) the intensity of cyclic conjugation in R .We now examinethe analogous effect of benzocyclobutadieno-annelation, and show that linear annelation strongly increasesthe cyclic conjugation in R, whereas the effect of angular annelation is negligibly small.
Chiral separation by ligand-exchange
Authors: Schmid Martin G , Gübitz Gerald
Published: December 2019

The principle of chiral ligand-exchange, introduced by Davankov, has become a widely used technique for chiral separation in both chromatography and in electromigration techniques. This simple technique makes use of the formation of mixed metal chelate complexes between a chiral selector and both enantiomers of an analyte. In HPLC, the chiral selector can be either bonded to the stationary phase or added to the mobile phase. In CE the chiral selector is simply added to the electrolyte. A relatively new approach represents CEC, where capillaries contain a chiral stationary phase. More than thousand papers appeared in the field of chiral ligand-exchange. To cite all papers would require several books.The present article gives an overview of both milestones and our activities on chiral separation using the principle of ligand-exchange. Recent advances in chip technology for chiral separations and new approaches regarding improvement of detection sensitivity are mentioned.
Volcanic periodicity plots along transition series, hypo-hyper-d-d-interelectronic correlations and electrocatalysis for hydrogen electrode reactions
Authors: Jakšić Jelena M. , Radmilović Velimir R. , Krstajić Nedeljko V. , Lacnjevać Časlav M. , Jakšić Milan M.
Published: December 2019

Volcano plots of various physical and chemical properties along transition series reveal the periodicity features of elements based on the d-d-electronic correlations, with rather similar equivalent shape, and consequently, when plotted into one another, yield various relevant linear interdependences. As the consequence, the d-band has been inferred and confirmed for the bonding, adsorptive and catalytic orbital. Such state of evidence leads to the conclusion that on the same way every hypo-hyper-d-d-interelectronic phase diagram behaves similar (local) volcano dependence as the part of the Periodic Table between two initial periods of interacting ingredients. In other words, their intermetallic phases of the same average d-electronic configuration replace the (‘missing’) elements in their energy state and behaviour in between, and consequently, have been used to assess the synergistically active electrocatalysts for the hydrogen electrode reactions from the peak values of the corresponding volcano plots. In the same context, the general hypsometric type of kinetic relations, including the Boltzmann-Maxwell distribution law that implies the exponential energy dependence, brings various energy states in mutual linear interdependence with the logarithm of the reaction rates.
Electrodeposition of Pd nanowires and nanorods on carbon nanoparticles
Authors: Bliznakov Stoyan , Vukmirovic Miomir , Sutter Eli , Adzic Radoslav
Published: December 2019

We report on the method for synthesizing palladium nanowires and nanorods involving the electrodeposition on oxidized amorphous carbon nanoparticles from chloride containing solutions. The effect of the deposition overpotential and the concentration of palladium ions on the morphology of the Pd electrodeposits have been established. Palladium grows predominately in the shape of nanowires if electrodeposited at potentials in the H underpotential deposition potential (UPD) range, where chloride ions are adsorbed only at the edges of nucleated monolayer-thick clusters on the carbon surface. The effect of the concentration of palladium ions on deposits’ morphology is also discussed. The mechanism of electrodeposition of Pd nanowires and nanorods in the H UPD potential range has been proposed.
Magnetron sputtered iridium oxide as anode catalyst for PEM hydrogen generation
Authors: Slavcheva Evelina P.
Published: December 2019

Thin films of iridium oxide are deposited by reactive magnetron sputtering. The influence of oxygen partial pressure in the sputtering plasma on the composition, surface structure and morphology of the films has been studied by XRD, SEM, AFM and XPS analysis. An optimal combination of sputtering parameters yields stable microporous amorphous films with highly extended fractal surface. The electrochemical properties of these films are investigated in view of their application as catalysts for PEM water splitting, using the electrochemical techniques of cyclovoltammetry and steady state polarization. A morphology factor assessing the catalyst active surface for a series of sputtered samples with varying thickness/loading is determined and correlated to the catalytic efficiency. It has been proven that iridium oxide is a very efficient catalyst for oxygen evolution reaction (OER). The best performance with anodic current density of 0.3 A cm–2; at potential of 1.55 V (vs. RHE) shows the 500 nm thick film containing 0.2 mg cm-2; catalyst. These results combined with the established long-term mechanical stability of the sputtered iridium oxide films (SIROFs) prove the advantages of the reactive magnetron sputtering as simple and reliable method for preparation of catalysts with precisely controlled composition, loading, and surface characteristics.
Environmental electrochemistry – importance and fields of application
Authors: Paunović Perica
Published: December 2019

The main goal of this paper is to present environmental electrochemistry as a very important field of environmental engineering which deals with protection and remediation of the Earth’s resources. The existing Earth’s environmental status as affected by a number of anthropogenic deteriorations is presented. Environmental electrochemistry has great potential to contribute to i) pollution detection, ii) remediation of polluted air, water and soils, iii) recycling of metals (saving of material resources) and alternative sources of energy (hydrogen economy).
A lag-time model for substrate and product diffusion through hydroxyethylcellulose gels used for immobilization of yeast cells
Authors: Velickova Elena , Kuzmanova Slobodanka , Winkelhausen Eleonora
Published: December 2019

Diffusion models were tested to select the most appropriate model for measuring the diffusion of glucose and ethanol trough hydroxyethylcellulose (HEC) cryogels. The lag-time model was selected as accurate, rapid and reliable for evaluating the diffusivity of the solutes. The diffusion coefficient of glucose through the HEC cryogel loaded with cells was estimated to be 6.9×10-6 cm2/s, while the diffusion coefficient of ethanol had a value of 2.5×10-5 cm2/s. The cells inside the gel matrix were not a barrier for the transport of the solute molecules. The diffusion properties of the cryogel were also examined in a real system. The parameters characterizing the repeated batch fermentation of glucose to ethanol by entrapped Saccharomyces cerevisiae cells gave evidence of very good diffusion properties of the HEC gel.
Development of a trap for fuel exhaust particulate matter under driving conditions and GC-MS method for their analysis
Authors: Todorović Dejan , Zdravkovski Zoran
Published: December 2019

Simple and useful GC/MS method was developed in order to analyze the toluene soluble components in particulate matter from diesel exhaust. Easily adaptable specially designed trap was built which could be mounted on exhaust pipe of different vehicles. It was filled with different materials on which particles were collected. After collection of the particles, the bare trap and different materials were washed and soaked with toluene. In some cases extraction process was speeded up with ultrasonification of the samples for 30 min. Samples were filtered and concentrated to 125‒500 ml and afterwards were directly analyzed by GC/MS. The separated components were identified by Automated Mass Spectral Deconvolution and Identification System (AMDIS) using a specialized user-built library. Five of the identified components[4-methylphenol, 3,3'-dichloro-1,1'-biphenyl, diethyl phthalate, 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester and mono(2-ethylhexyl) ester of 1,2-benzenedicarboxylic acid] were found in the European priority lists (Category 1 and Category 2) of endocrine disruptors.
A simple isocratic RP-HPLC method for quality control of oseltamivir capsules
Authors: Ameti Agim , Slavkovska Jasmina , Starkoska Katerina , Arsova-Sarafinovska Zorica
Published: December 2019

A simple isocratic reversed-phase high performance liquid chromatographic (RP-HPLC) method was developed for determination of oseltamivir active pharmaceutical ingredient (API) in bulk drug and pharmaceuticals. The separation was achieved on a Purospher STAR® RP – 18e column with a mobile phase consisting of methanol- 0.02 mol l-1 phosphate buffer, pH 5, 50:50 (v/v). Chromatographic results demonstrated the specificity of the method for determination of oseltamivir in presence of degradation products generated in studies of forced decomposition. The limit of detection (LOD) and limit of quantification (LOQ) for oseltamivir phosphate were 0,0162 μg ml-1 and 0,0491 μg ml-1, respectively. The advantages of this method include simple sample treatment and short elution time (less than 6 min). Furthermore, using methanol instead of acetonitrile in a mobile phase composition considerably reduces the laboratory expenses, still retaining adequate sensitivity for routine analysis as well as for evaluation of potentially counterfeit Tamiflu® products.
On the differential hydration of various forms of glycine in diluted aqueous solutions: a Monte Carlo study
Authors: Bujaroska Biljana , Stojanoski Kiro , Pejov Ljupco
Published: December 2019

Rigid-body Monte Carlo simulations were carried out to study the differential hydration of zwitterionic and neutral forms of glycine in water. To account for the solute polarization by the rather polar liquid environment, initial geometries were chosen as minima on the MP2/aug-cc-pVTZ potential energy surfaces of neutral and zwitterionic glycine continuously solvated by water, implementing the polarizable continuum model (PCM) within the integral equation formalism (IEFPCM). The dynamically changing hydrogen bonding network between the solute and solvent molecules was analyzed imposing distance, energy and angular distribution-based criteria. It was found that, on average, the zwitterionic form of glycine acts as an acceptor of 4.53 hydrogen bonds, while it plays the role of a proton donor in (on average) 2.73 hydrogen bonds with the solvent water molecules. In particular, we have found out that 2.73 solvent water molecules are involved in hydrogen bonding interaction with the ammonium group, acting as proton-acceptors. This is in excellent agreement with the recent experimental neutron diffraction studies, which have indicated that 3.0 water molecules reside in the vicinity of the NH3+ group of aqueous zwitterionic glycine. Neutral form of aqueous glycine, on the other hand, on average donates protons in 1.63 hydrogen bonds with the solvent water molecules, while at the same time it accepts 2.53 hydrogen bonds from the solvent molecules. The greater charge polarization in the zwitterionic form thus makes it much more exposed to hydrogen bonding interaction in polar medium such as water, which is certainly the main reason of the larger stability of this form of glycine in condensed media.
Electrophoretic deposition of alumina and boehmite coatings on metal surfaces
Authors: Miskovic-Stankovic Vesna
Published: December 2019

Electrophoretic deposition (EDP) is gaining increasing attention both in science and industry, due to novel applications in the processing of advanced ceramic materials and ceramic coatings. Electrophoretic deposition has become very interesting because this method has allowed the formation of thin films or multilayer films of controlled thickness and morphology, enabling the formation of films on substrates of complex geometry, aimed for different applications. This review paper represents the mechanism of electrodeposition of ceramic coatings (alumina and boehmite coatings) on metal surfaces, as well as the determination of the optimal deposition parameters (applied voltage, deposition time, electrodeposition bath temperature, suspension concentration) in order to control the thickness and morphology of deposited films. It was shown that coatings of maximum thickness, low porosity and good adhesion were obtained at lower deposition voltages and for longer deposition times.
Behavior of transport and separation of lanthanum, yttrium and lutetium metal ions through celluose fiber supported solid membrane
Authors: Gaikwad Abaji G
Published: December 2019

A novel idea explored was to study the behavior of transport and separation of lanthanum, yttrium and lutetium metal ions by using cellulose fiber supported solid membrane. The cellulose fiber membrane was prepared by chemical modification of cellulose fiber by esterification reaction with citric acid. Different experimental variables such as time variation, membrane length, stirrings of source and receiving phase, pH of source phase, different stripping agents  such as nitric acid, hydrochloric acid, sodium nitrate, ammonium thoicyanate, D2EHPA, TBP, Aliquat-336, tartaric acid, EDTA, organic solvents, etc in receiving phase were explored. Pre-concentration of lanthanum, yttrium and lutetium metal ions from dilute solution was carried out.
Chemical and sensorial characteristics of fruit spirits produced from different black currant (Ribes nigrum l.) and red currant (Ribes rubrum l.) cultivars
Authors: Vulić Todor , Nikićević Ninoslav , Stanković Ljubiša , Veličković Milovan , Todosijević Marina , Popović Branko , Urošević Ivan , Stanković Miroslava , Beraha Isidora , Tešević Vele V
Published: December 2019

Chemical characteristics of fruit spirits produced from three black currant cultivars (Malling Juel, Ometa, Ben Sarek) and two red currant cultivars (Rondom and Versailles) grown in Serbia were examined using gas chromatography. In addition, sensory evaluation of the spirit samples was performed using the Buxbaum model of positive rating. Fruit spirits produced from black currant cultivars displayed the highest contents of methanol (267.2 - 595.0 g/hl A. A) and amyl alcohols (74.2 - 204.8 g/hl A. A). Total sensory scores of currant brandies ranged between 17.60 and 18.40, while currant brandy produced from Ben Sarek black currant cultivar received the highest score (18.40). All tested samples of currant brandies fulfilled EU requirements as regards their content of methanol and other components such as acetaldehyde, ethyl acetate and high alcohols. The currant distillates were compared with other commercial spirits, including plum and grape brandies.
Production of 1,3-propanediol by Clostridium butyricum DSM 5431 in an Anaerobic Moving-Bed Bioreactor
Authors: Suratago Teerawat , Nootong Kasidit
Published: December 2019

Production of 1,3-propanediol (PD) by Clostridium butyricum DSM 5431 was investigated in a moving-bed bioreactor with BCN-009 as the cell-supporting material. The results of steady state operation indicated that PD production in a moving-bed bioreactor was feasible. The moving-bed bioreactor provided good liquid mixing, resulting in a suitable pH range (i.e., pH = 6.9 – 7.0) throughout the experiment. Maximum PD concentration (33.8 g/L), product yield (0.7), and productivity (16.9 g/L/h) were obtained when the bioreactor was operated using an inlet glycerol concentration and a dilution rate of 60 g/L and 0.5 h-1, respectively. Finally, we conclude that moving-bed bioreactors are attractive for future development as seen by higher effluent PD concentrations and productivity compared to other suspended-growth and immobilized bioreactor configurations.
Total and extractable forms of Cu, Zn, Ni, Cr, and Fe in vineyard soil (Valandovo valley, Macedonia) determined by a sequential extraction procedure
Authors: Karakaseva Elizabeta , Boev Blazo , Zajkova Vesna
Published: December 2019

The total and extractable forms of Cu, Zn, Pb, Ni, Cr, and Fe in vineyard soils from Valandovo valley were analyzed in order to understand the existence of metals in soils and their potential availability to the flora and fauna. The metals (Cu, Zn, Ni, Pb, Cr, and Fe) in soil was determined by by ICP-EAS and sequential extraction procedure [5]. Other chemical and physical properties such as pH, CEC (cation exchange capacity), organic matter, carbonate and particle size of soils collected from vineyards plots were also analyzed. The total concentrations of Cu, Zn, Pb, Ni, Cr, and Fe in almost all soil samples does not exceed the maximum permissible concentrations (MPC) of trace elements in agricultural soils proposed by Kabata-Pendias and Pendias (2001). The only exception was the soil sample R (3), where higher concentrations were measured especially for Fe, Ni and Cr, and to a lesser extent Cu and Zn. Sequence extraction shows that the distribution of metals increase in order: oxidisable (e.g., organic substance and sulphides) > fraction bound in the crystal lattice of silicate minerals (residual fraction) > reducible (e.g., iron/manganese oxides) > exchangeable, water and acid soluble (e.g., carbonates). The prevalence of metals in oxidisable fraction in the soil shows that this fraction has a dominant role in controlling the behavior and transport of these metals in soil. The low levels of metals in exchangeable and carbonate bound fraction (Ni (7,5%)>Pb (3,5%)> Cu (2,6%)> Zn (2,2%)> Cr (0,2%)) indicates a low rate of activity and mobility of these metals in soil solution caused by the current physico-chemical conditions in soil.
Voltammetric behavior and determination of the bronchodilator doxofylline at a boron-doped diamond electrode
Authors: Saxena Sachin , Shrivastava Ratnanjali , Satsangee Soami P.
Published: December 2019

The electrochemical behavior of the asthma drug doxofylline was studied at a boron-doped diamond electrode in BR buffer (pH 3.8) by square-wave voltammetry. Cyclic voltammetry revealed the oxidation of doxofylline as an irreversible diffusion-controlled process. The oxidation mechanism was proposed and the drug was studied in the presence of solubilized systems like Tween-20 (T-20), sodium dodecyl sulfate (SDS), Triton X-100 (TTN), dioxane (DO), dimethylformamide (DMF), diethyl ether (DEE), benzene and methanol (MeOH). Comparison of the current responses in the solution system explained the sensitivity of the boron-doped diamond electrode (BDDE) with a three-fold increase in the current value compared to that of a glassy carbon electrode (GCE) at a fixed concentration of doxofylline. Peak current values varied linearly with increasing concentration and the LOD and LOQ were found to be 3.48 and 10.56 µg/ml, respectively. This method was employed to investigate doxofylline in the pharmaceutical formulation.
Artemisinins and synthetic peroxides as highly efficient antimalarials
Authors: Opsenica Dejan Milos , Šolaja Bogdan Aleksandar
Published: December 2019

Malaria is devastating disease and global public health problem, with nearly half world population exposed to risk. Illness is caused by five Plasmodium species, P. falciparum, P. ovale, P. vivax, P. malarie and P. knowlesi, from which P. falciparum is the most serious one causing cerebral malaria and is the major reason for malaria mortality. Vaccine against malaria is not expected in the near future and chemotherapy remains as most feasible alternative for treatment of the disease. The development of widespread drug-resistance to chloroquine (CQ), the most successful antimalarial drug up to date, has resulted in severe health issues for countries in malaria endemic regions. Organic peroxides, like artemisinins, 1,2,4-trioxanes, 1,2,4-trioxolanes, 1,2,4,5-tetraoxanes and their chimeras, are the best choice for malaria treatment nowadays.  These therapeutics are fast acting, non-toxic, low costing and without reported data of parasite resistance. Stability of peroxide bonds enables synthetic comfort and resulting in diversity of synthesised structures. The most important classes of peroxide antimalarials with promising representatives are reviewed and possible mechanisms of action were presented in details.
Phenyl-cyclopentadienyl rule
Authors: Đurđević Jelena , Gutman Ivan
Published: December 2019

Within a systematic study of cyclic conjugation in the benzo-annelated derivatives of acenaphthylene and fluoranthene, a general regularity was discovered, named phenyl-cyclopentadienyl rule (PCP rule). According to this rule, six-membered rings connected to the five-membered ring by a single carbon-carbon bond increase the magnitude of cyclic conjugation in the five-membered ring. The greater the number of such six-membered rings is, the stronger the cyclic conjugation in the five-membered ring. The PCP rule was initially established by studying the energy effects of individual rings, and was eventually corroborated by a variety of other independent approaches (Wiberg bond orders, carbon-carbon bond lengths calculated by high-level ab initio DFT methods, multicenter delocalization indices, ring currents).
Simultaneous determination of acesulfame-K, aspartame and stevioside in sweetener blends by ultraviolet spectroscopy with variable selection by sipls algorithm
Authors: He Yang-Chun , Fang Sheng , Xu Xue-Jiao
Published: December 2019

A chemometric-assisted UV absorption spectroscopic method is proposed for the simultaneous determination of acesulfame-K, aspartame and stevioside in raw powder mixtures of commercial sweeteners. The synergy interval partial least squares (siPLS) algorithm was applied to select the optimum spectral range and their combinations. The utilization of spectral region selection aims to construct better partial least squares (PLS) model than that established from the full-spectrum range. The results show that the siPLS algorithm can find out an optimized combination of spectral regions, yielding lower relative standard error of prediction (RSEP) and root mean square error of prediction (RMSEP), as well as simplifying the model. The RMSEP and RSEP obtained after selection of intervals by siPLS were 0.1330 μg·ml–1 and 1.50 % for acesulfame-K, 0.2540 μg·ml–1 and 1.64 % for aspartame, 1.4041 μg·ml–1 and 2.03 % for stevioside respectively. The recovery values range from 98.12 % to 101.88 % for acesulfame-K, 98.63 % to 102.96% for aspartame, and 96.38 % to 104.04 % for stevioside respectively.
Optimization of hydrophilic interaction liquid chromatographic method for simultaneous determination of cetylpyridinium chloride and benzocaine in lozenges
Authors: Nakov Natalija , Acevska Jelena , Brezovska Katerina , Petkovska Rumenka , Dimitrovska Aneta
Published: December 2019

A new Hydrophilic Interaction Liquid Chromatography (HILIC) method was developed for simultaneous determination of cetylpyridinium chloride and benzocaine as active substances in lozenges. Method development included investigation of the influence of the critical chromatographic conditions such as: type of organic modifier, mobile phase strength, ionic strength and pH value of the buffer used in the mobile phase, as well as experimental determination of dominant mechanism of retention. The optimal chromatographic conditions were obtained using bare silica column and a mobile phase consisting of acetonitrile and ammonium formate (50 mM, pH = 4.0) in ratio 80 : 20 V/V. The method was validated in terms of specificity, linearity, accuracy and precision. The validation results indicate that the proposed HILIC method is suitable for quantitative analysis of cetylpyridinium chloride and benzocaine in lozenges.
Thermal and optical properties of new poly(amide-imide)-nanocomposite reinforced by layer silicate based on chiral n-trimellitylimido-L-valine
Authors: Faghihi Khalil , Soleimani Masoumeh , Nezami Shabnam , Shabanian Meisam
Published: December 2019

Two new samples of poly(amide-imide)-montmorillonite reinforced nanocomposites containing N-trimellitylimido-L-valine moiety in the main chain were synthesized by a convenient solution intercalation technique. Poly(amide-imide) (PAI) 5 as a source of polymer matrix was synthesized by the direct polycondensation reaction of N-trimellitylimido-L-valine (3) with 4,4′-diaminodiphenyl ether 4 in the presence of triphenyl phosphite (TPP), CaCl2, pyridine and N-methyl-2-pyrrolidone (NMP). Morphology and structure of the resulting PA-nanocomposite films (5a) and (5b) with 10 and 20 % silicate particles were characterized by FTIR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of clay dispersion and the interaction between clay and polymeric chains on the properties of nanocomposite films were investigated by using Uv-vis spectroscopy,  thermogravimetric analysis (TGA) and water uptake measurements.
Study of the mechanism of nitrophenols sorption on expanded perlite ‒ equilibrium and kinetics modelling
Authors: Yaneva Zvezdana , Koumanova Bogdana , Georgieva Nedyalka
Published: December 2019

The adsorption behavior of 2-nitrophenol (2-NP) and 2,4-dinitrophenol (2,4-DNP) on expanded perlite (EP) at equilibrium and kinetic conditions was investigated. The experimental equilibrium data were interpreted by Langmuir, Freundlich, Redlich–Peterson, Temkin and the multilayer isotherm models. Both the Temkin and the multilayer models gave the most satisfactory representation of the experimental data for 2-NP sorption on EP covering the whole concentration range, presuming high initial sorption rate, presence of adsorbent-adsorbate chemical interactions and multilayer adsorption, as the basic characteristics featuring the equilibrium behavior of the system studied. The experimental kinetic results were analyzed by the pseudo-first, pseudo-second order models, Bangham’s model, intra-particle diffusion model, and Elovich kinetic equation. The values of the calculated rate, mass transfer parameters and correlation coefficients proved that chemisorptions/intraparticle diffusion could be outlined as the basic rate controlling mechanisms during 2-NP/2,4-DNP sorption on expanded perlite. Uptake of nitrophenols increased in the order 2-NP < 2,4-DNP.
Microencapsulation of Lactobacillus casei in chitosan-Ca-alginate microparticles using spray-drying method
Authors: Petreska Ivanovska Tanja , Petruševska-Tozi Lidija , Dabevska Kostoska Margita , Geškovski Nikola , Grozdanov Anita , Stain Chris , Stafilov Trajče , Mladenovska Kristina
Published: December 2019

In this study, the probiotic Lactobacillus casei was microencapsulated using the method of spray-drying combined with polyelectrolyte complexation of alginate, fructooligosaccharide and chitosan, and cross-linking with calcium chloride, followed by freeze-drying. Survival rate and physicochemical properties of the prepared microparticles were evaluated. In addition, viability of Lactobacillus casei in simulated gastric and intestinal juices was investigated. Positively charged microparticles with average size of 11.08±1.1 μm and high cell viability of 10.98±0.11 log cfu/g were prepared. The synbiotic microparticles were stable during exposure to simulated gastric and intestinal juices, while release of viable cells above the therapeutic value (8.31±0.14 log cfu/g) in the simulated colonic pH was observed.The presented method for microencapsulation of synbiotics shows potential for effective protection of viable probiotic cells during exposure to harsh environmental conditions.
New convenient vapor pressure-temperature correlation for some aliphatic hydrocarbons
Authors: Bogdanov Jane B , Bogdanov Bogdan
Published: December 2019

New empirical equations for correlating temperature dependence of vapor pressure for C6-C20 aliphatic hydrocarbons are proposed: ln(VP) = k1·T/(k2+T) where, VP – vapor pressure, T – temperature, k1 – asymptotic maximum vapor pressure, and k2 – temperature at which the vapor pressure has half of its maximum value. Descriptors k1, k2 and k1/k2 have physical meaning and are unique for a given liquid. This “uniqueness” can be exploited for quantitative description of vapor pressure-temperature curve. The equation given above can be transformed algebraically into other convenient forms for plotting experimental data such as: T/ln(VP) = intercept + slope·T k1 = 1/slope; k2 = intercept/slope These derived descriptors can be utilized for evaluation and comparison of properties of different liquids and liquid mixtures and can serve as additional parameters for analysis of liquid hydrocarbon-based fuels for internal combustion engines.
Effect of the electrolysis regime on the structural characteristics of honeycomb-like electrodes
Authors: Nikolic Nebojsa D. , Branković Goran , Pavlović Miomir G.
Published: December 2019

The effect of different current regimes of electrolysis on the micro- and nanostructural characteristics of open porous structures was examined by the analysis of honeycomb-like copper electrodes obtained by constant galvanostatic (DC) electrodeposition and by regimes of pulsating (PC) and reversing (RC) current. An increase in the number of holes formed by detached hydrogen bubbles, the decrease in wall width between holes and changes in surface morphology around holes from cauliflower-like agglomerates of copper grains to dendrites were observed in the following order: the DC, PC and RC regime. The hole size formed in the RC regime was smaller than the hole size formed in the DC and PC regimes. Analysis of the obtained structural characteristics showed that the specific surface area of the honeycomb-like electrodes was increased by the application of the PC and RC regimes in relation to the DC regime.
Air pollution study in Macedonia using a moss biomonitoring technique, ICP-AES and AAS
Authors: Barandovski Lambe , Stafilov Trajce , Sajn Robert , Frontasyeva Marina , Baceva Katerina
Published: December 2019

In the framework of the International Cooperative Programme on Effects of Air Pollution on Natural Vegetation and Crops under the auspices of the United Nations Economic Commission for Europe (UNECE-ICP Vegetation) Convention on Long-Range Transboundary Air Pollution (LRTAP), in 2002 and 2005, a moss biomonitoring technique was applied to air pollution studies in the Republic of Macedonia. The third moss survey took place in August and September 2010 when 72 samples of the terrestrial mosses Homalothecium lutescens and Hypnum cupressiforme were collected over the territory of the Republic of Macedonia, using the same sampling network grid as for the previous surveys. Using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and atomic absorption spectrometry (AAS), a total of 18 elements (Al, Ba, Ca, Cd, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Ni, P, Pb, Sr, V and Zn) were determined. To reveal hidden multivariate data structures and to identify and characterize different pollution sources, Principal Component Analysis was used. Distributional maps were prepared to point out the regions most affected by pollution and related to known sources of contamination. As in the previous surveys, the regions near the towns of Skopje, Veles, Tetovo, Radoviš and Kavadarci were found to be most affected by pollution, even though the median elemental content in the mosses in 2010 for  Cd, Cr, Cu, Ni, Pb and Zn was slightly lower than in the previous surveys. For the first time, P content in the moss samples was analyzed, and a higher content of this element as well as K in the mosses was observed in the agricultural regions of the country.
Minerals from the Republic of Macedonia with an introduction to mineralogy
Authors: Pekov Igor V
Published: December 2019

The reviewed monograph is the first extended work in which data on the minerals of the Republic of Macedonia have been described. This book is written in English to make the information on the mineralogy of the Republic of Macedonia accessible to a worldwide audience. The monograph contains a general introduction to mineralogy, which makes it useful for people starting their education in this science, i.e. students of geology, amateur mineralogists and mineral collectors in the Republic of Macedonia. Thus, the monograph is a dual-purpose book.
Synthesis and coordination chemistry of thiophenol-based heterodonor ligands containing P,S, As,S and P,SAs donor atoms
Authors: Sárosi Imola , Silaghi-Dumitrescu Luminiţa , Hey-Hawkins Evamarie
Published: December 2019

This review article describes the synthesis and coordination chemistry of three types of thiophenol-based heterodonor ligands containing tertiary phosphine and/or arsine groups in combination with sulfur. Phenylthio(diphenyl)phosphine and -arsine ligands, EPh2(SPh) (E = P, As), incorporate an E–S bond in their structures. Upon reaction with different metal carbonyls, metal-mediated cleavage of the E–S bonds of these ligands has been observed, leading to a variety of sulfur- and phosphorus- or arsenic-containing metallacycles. The structurally isomeric phosphino- and arsinoarylthiols HSC6H4-2-EPh2 (ESH) combine a phosphine or arsine centre with a thiol functionality, which is usually deprotonated on coordination. These compounds have been shown to be very versatile ligands that form stable complexes with a wide range of transition metals. The heterotopic ligand 1-Ph2AsSC6H4-2-PPh2 (P,SAs) not only combines the properties of phenylthio(diphenyl)arsine and 2-diphenylphosphanylbenzenethiol by incorporating all three donor atoms in its structure, but also allows the effect of the PPh2 group in the ortho position on the cleavage of the As–S bond to be studied.
Rapid method for evaluation of cure kinetics of thermoseting polymers
Authors: Bogoeva-Gaceva Gordana , Buzarovska Aleksandra
Published: December 2019

AbstractIn this study we report the results of a rapid method applied for evaluation of the data obtained by DSC measurements of cure reaction of thermosetting resins. The method is based on Borchardt and Daniels kinetic model and enables determination of basic parameters important for product and process development, but also for optimization of cure cycles for variety of thermosets.
Broccoli isothiocyanates content and in vitro availability according to variety and origin
Authors: Rodríguez-Hernández M. Carmen , Medina Sonia , Gil-Izquierdo Angel , Martínez-Ballesta Carmen , Moreno Diego A.
Published: December 2019

Broccoli is considered one of the healthiest vegetables own to its high content of beneficial biologically active compounds – the breakdown products of the glucosinolates, the isothiocyanates. The aim of this work was to characterize the production of isothiocyanates (sulforaphane and iberin and related metabolites) from different sources of glucosinolates by means of comparison between different broccoli cultivars and commercial samples, investigating their composition and in vitro bioavailability. Differences in the major intact glucosinolates were observed between the different experimental and commercial samples showing lower concentrations of glucosinolates the latest. The simulation of digestion reduced the concentration of parental phytochemicals (glucosinolates) producing the hydrolysis to biologically active isothiocyanates. The commercial samples showed lower levels of ITCs than experimental broccoli cultivars. Measurement of the glucosinolates ingested by UPLC-QqQ-MS/MS has allowed an exact quantifying of these compounds, particularly isothiocyanates, which will help to futures cancer chemoprevention studies.
Synthesis and structure of (R,S)-2-methyl-4-(4-nitrophenyl)-pyrano[3,2-c]chromen-5(4H)-one
Authors: Nikolova Rosica P. , Shivachev Boris , Mikhova Bozhana , Stamboliyska Bistra , Mladenovska Kristina , Panovska Ana P. , Popovski Emil
Published: December 2019

In this paper, the synthesis and structure of a novel pyrano[3,2-c]coumarin, which was obtained unexpectedly in a reaction of phosphoryl chloride and acenocoumarol, are presented. The chemical structure of the novel compound was elucidated by a detailed spectroscopic analysis based mainly on 1D and 2D NMR techniques. The structure was finally confirmed with a single-crystal X-ray analysis. The B3LYP/6-311+G** method correctly reproduces the bond lengths, bond angles, torsion angles, and other experimental spectroscopic data, which can be useful for investigating the characteristics of some structurally related molecules. Additionally, the title compound was obtained in high yields by performing a dehydratation reaction of acenocuomarol with acetic anhydride.
Optimization and development of SPE-HPLC-DAD method for the determination of atrazine, malathion, fenitrothion and parathion pesticide residues in apple juice
Authors: Velkoska-Markovska Lenche , Petanovska-Ilievska Biljana
Published: December 2019

ultraviolet–diode array detection (UV-DAD) for the simultaneous determination of atrazine, malathion, fenitrothion, and parathion residues in apple juices has been developed. For the enrichment and cleanup of compounds of interest, Supelclean ENVI-18 SPE tubes were used. Separation and quantitative determination of the analytes were performed on a LiChrospher 60 RP-select B (125 mm × 4 mm, 5 μm, Merck) analytical column, the mobile phase consisting of acetonitrile/water (55/45, V/V) in isocratic elution with the following set values: flow rate of 1 ml/min, constant column temperature at 25 oC, and UV detection at 220 nm and 270 nm. The gathered values of the investigated pesticides from the apple juice samples were in the range 94.2 %–117.2 %.
Morphology and fractal dimension of TiO2 thin films
Authors: Petrović Srdjan P
Published: December 2019

The influence of annealing temperature on the morphology and surface fractal dimension of titanium dioxide (TiO2) films prepared via the spray deposition process was investigated. Thin films with various morphologies were obtained at different temperatures and characterized by X-ray diffraction and atomic force microscopy (AFM). It was found that the crystalline structure of TiO2 films depends strongly on annealing temperature. At higher temperatures, the partial phase transformation of anatase-to-rutile was observed. The morphology and surface fractal dimensions were evaluated by image analysis methods based on AFM micrographs. The results indicate that the value of surface roughness (the standard deviation of the height values within the given area of AFM image) of TiO2 films increases with increasing annealing temperature. Fractal analysis revealed that the value of the fractal dimension of the samples decreases slowly from 2.23 to 2.15 following the annealing process.
Biocomposites based on poly(lactic acid) and kenaf fibers: Effect of micro-fibrillated cellulose
Authors: Bogoeva-Gaceva Gordana , Dimeski Dimko , Srebrenkoska Vineta
Published: December 2019

In this work, the influence of microfibrillated cellulose (MFC) on the basic mechanical properties of PLA/kenaf fiber biocomposites has been studied. The addition of 5–15 % microfibrillated cellulose to a biocomposite premix has resulted in an increased glass transition temperature of the final product, produced by compression molding of previously melt-mixed composite components. The presence of MFC has influenced the interface-sensitive properties of the PLA/kenaf composite: at an optimal loading of 10 %, the interfacial energy release rate was increased by about 20 %. Moreover, flexural strength and modulus of the composites were also improved (from 34.8 MPa to 57.1 MPa and from 4.9 GPa to 5.8 GPa, respectively).
News - Вести
Authors: Editors Editors
Published: December 2019

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