Electrochemical determination of histamine

U ovom radu su razvijene elektrohemijske metode za određivanje histamina. U svim elektrohemijskim ispitivanjima korišćena je hronopotenciometrija. Istraživanja su obuhvatila optimizaciju uslova elektroanalitičkih tehnika i upoređivanje mehanizama generisanja analitičkog signala primenom različitih radnih elektroda, razvoj odgovarajućeg postupka pripreme uzoraka za analizu i samo određivanje histamina u hrani i piću. Ispitana je mogućnost primene čvrste zlatne elektrode, tankoslojne živine i tankoslojne niklove elektrode za elektrohemijsko određivanje histamina. U slučaju elektrooksidacije histamina, razjašnjeni su mehanizmi generisanja signala na primenjenim elektrodama. Optimizacija uslova elektroanalitičkih tehnika obuhvatila je odabir odgovarajućeg pomoćnog elektrolita i njegove koncentracije, ispitivanje uticaja početnog potencijala i struje oksidacije na analitički signal analita. Pored toga, za svaki elektrohemijski sistem definisana su osetljivost i reproduktivnost, selektivnost, kao i opseg linearnosti. Primenom tankoslojne niklove elektrode uočena je pojava adsorpcionog koncentrovanja analita, te su u slučaju ovog elektrohemijskog sistema ispitani i uticaji vremena adsorpcije i temperature ispitivanog medijuma na analitički signal histamina. Na tankoslojnoj živinoj elektrodi analitički signal se generisao usled direktne oksidacije histamina primenom konstantne struje. Na ostale dve elektrode, pored elektrodnih reakcija odvijale su se i hemijske reakcije, tako da se oksidacija histamina u oba slučaja odigravala po ECE mehanizmu (elektrodna reakcija – hemijska reakcija – elektrodna reakcija). Na čvrstoj zlatnoj elektrodi, generisanje signala je bilo posledica oksidacije histamina elektrogenerisanim hlorom, dok se u slučaju tankoslojne niklove elektrode radilo o kombinovanoj katalitičko‐adsorpcionoj hronopotenciometriji. Tankoslojna živina elektroda je pokazala dobru selektivnost pri koncentracijama aminokiselina i histamina nižim od 5 mg/dm3, dok je pri višim koncentracijama dolazilo do preklapanja analitičkih signala. Ostali elektrohemijski sistemi nisu pokazali odgovarajuću selektivnost. Najveća osteljivost je ostvarena primenom tankoslojne niklove elektrode (LOD = 0,11 mg/dm3), zatim sledi čvrsta zlatna elektroda (LOD = 0,27 mg/dm3) i na kraju tankoslojna živina elektroda (LOD = 1,31 mg/dm3). U okviru definisanja postupka pripreme uzoraka, ispitana je efikasnost različitih ekstrakcionih tehnika i različitih ekstragenasa u pogledu izdvajanja histamina iz uzoraka. Pored toga razvijeni su odgovarajući postupci prečišćavanja ekstrakata primenom preparativnih hromatografskih tehnika, i to na tankom sloju i na stubu adsorbensa. Po definisanju optimalnih uslova elektrohemijskog određivanje histamina, kao i razvijanja postupka pripreme uzoraka, histamin je određen u različitoj hrani i piću.In this work, the electrochemical methods for the determination of histamine were developed. All electrochemical investigations were carried out by chronopotentiometry. The research included optimization of the experimental parameters of electroanalytical techniques and comparison of the mechanism of the analytical signal generation by using the different working electrodes. Upon the development of sample preparation procedure, histamine was determined in different food and beverages. The possibility of applying solid gold electrodes, thin film mercury electrode and thin film nickel electrode for electrochemical determination of histamine was examined. The mechanisms of histamine electrooxidation on different working electrodes were explained and elaborated. Optimization of the experimental parameters of electroanalytical techniques included the selection of appropriate supporting electrolyte and its concentration, and investigation of the influence of initial potential and oxidation current on histamine analytical signal. Beside this, for each electrochemical system sensitivity and reproducibility, selectivity as well as linearity range were defined. The use of thin nickel film electrode resulted in adsorptive accumulation, and in that case the effects of accumulation time and medium temperature on histamine analytical signal were defined. On thin film mercury electrode, histamine analytical signal was generated due to direct oxidation of histamine by a constant current. On other two electrodes, electrode reactions were coupled with chemical reaction, and histamine oxidation was by ECE mechanism (electrode reaction – chemical reaction – electrode reaction). On solid gold electrode histamine was oxidized indirectly by electrogenerated chlorine, while in the case of thin film nickel electrode combination of catalytic and adsorptive chronopotentiomety was responsible for signal generation. Thin film mercury electrode showed good selectivity for histamine and amino acids concentrations below 5 mg/dm3, but higher concentrations caused the overlapping of analytical signals. Other electrochemical systems did not show adequate selectivity. The best sensitivity was achived by thin film nickel electrode (LOD = 0.11 mg/dm3), followed by a solid gold electrode (LOD = 0.27 mg/dm3), and by thin film mercury electrode (LOD = 1.31 mg/dm3). In order to define adequate sample preparation procedure, the efficiency of different extraction techniques and different solvents were tested for histamine extraction from the samples. Appropriate procedures for purification of extracts were defined as well, by applying preparative thin layer and column chromatography. After optimization of the electrochemical methods for histamine determination, as well as the procedure of sample preparation, developed methods were applied for histamine determination in various food and beverages

Identifikacija i kvantifikacija gljiva u travno-leguminoznoj silaži

Objective of the research was to determine the presence, total count and species of fungi in samples of grass-leguminous silages depending on the botanical composition of mixture, nitrogen fertilization and crop utilization phase. Most of identified fungi species are of Fusarium genus (80-91%). In analyzed samples of silage total fungi count in average for three year period of research (2005-2007) was 2.31-3.09 log10 CFU g-1 and it varied depending on the investigated factors. Factor of type of mixture had significant effect on fungi count in first two investigation years, whereas nitrogen fertilization caused variations in fungi count in the first and third investigation year. Cutting in early utilization phases statistically significantly influenced total fungi count only in one investigation year (2006).Cilj istraživanja je bio da se odredi prisustvo, ukupan broj i vrste gljiva u uzorcima silaža travno-leguminoznih smeša u zavisnosti od botaničkog sastava smeše, đubrenja azotom i faze iskorišćavanja useva. Većinom su identifikovane vrste gljiva iz roda Fusarium (80-91%). U ispitivanim uzorcima silaže ukupan broj gljiva u proseku za trogodišnji period istraživanja (2005-2007) je bio od 2.31-3.09 log10 CFU g-1 i varirao je u zavisnosti od ispitivanih faktora. Faktor vrsta smeše je značajno uticao na broj gljiva u prve dve godine istraživanja, dok je đubrenje azotom prouzrokovalo variranja u broju gljiva u prvoj i trećoj godini istraživanja. Kosidba u ranijim fazama iskoršćivanja statistički značajno je uticala na ukupan broj gljiva samo u jednoj godini istraživanja (2006)

Dinamika pojave i učestalosti populacija Fusarium vrsta na uskladištenom zrnu kukuruza

Production and providing of high quality maize grain are of primary importance for livestock production since maize is the main component of livestock feed. Contamination with fungi not only diminishes the quality of grain, but some fungi species can produce highly toxic compounds known as mycotoxins. Considering that maize is economically the most important grown plant in Serbia, content and intensity of frequency of these pathogen fungi species are investigated in maize stored in the storage facilities. Based on studies of the fungi incidence in stored maize intended for nutrition of livestock, it was established that during the period from February 2005 to March 2006, some fungi species were present successively (Fusarium spp., Penicillium spp.), other with interruptions of one (Nigrospora spp., Aspergillus spp., Acremonium spp., Alternaria spp), three (Mucor spp., Chaetomium spp., Rhizopus spp.) to four months (Cladosporium spp.), and also sporadically during three (Epicoccum spp., Rhizopus spp., Trichothecium spp.), two (Gliocladium spp.) or one month (Papulaspora spp., Phialophora spp.). Period June-October is the most critical for preservation of the quality of stored maize since the number of fungi species present (8−14 of total of 17 identified fungi genera) and their frequency during this period are the highest, especially of toxigenic species of Fusarium (43.5−62.5%) and Penicillium (10.0−33.5%) genera. Positive correlation (r = 0.5979**) between dynamics of incidence and frequency of isolated fungi species indicates that fungi with higher frequency of incidence remain longer on the grain during storage. F. verticillioides and F. subglutinans, of total of 6 identified Fusarium species were present on the grain during entire year and with the highest frequency (24.7% and 5.9%, respectively). During single year (2005) F. verticillioides was present in the highest percentage from February to October (22.0−39.5%), and F. subglutinans from April to October (8.0−12.5%), whereas the both species were isolated the least during winter period December-January (4.0−8.0% and 0.5−1.0%, respectively). F. graminearaum is the third toxigenic Fusarium species which from the mycotoxicological aspect can be important for period June-September when it is mostly present (5.0−11.0%). Incidence of other Fusarium species is sporadic (1.3% F. proliferatum, 1.0% F. sambucinum and 0.5% F. poae).Proizvodnja i obezbeđivanje visokog kvaliteta zrna kukuruza su od primarnog značaja za stočarsku proizvodnju jer je kukuruz osnovna komponenta stočne hrane. Zaraza gljivama ne samo da smanjuje kvalitet zrna, već neke vrste gljiva mogu produkovati visoko toksična jedinjenja, poznata kao mikotoksini. S obzirom da je kukuruz ekonomski najvažnija gajena biljka u Srbiji, sadržaj i intenzitet učestalosti ovih patogenih vrsta gljiva se ispituje u kukuruzu u skladištu. Na osnovu proučavanja pojave gljiva na uskladištenom kukuruzu, koji je bio namenjen za ishranu životinja, utvrđeno je da su u periodu od februara 2005. do marta 2006. godine neke gljive prisutne sukcesivno (Fusarium spp., Penicillium spp.), druge diskontinuirano sa prekidom od jednog (Nigrospora spp., Aspergillus spp., Acremonium spp., Alternaria spp), tri (Mucor spp., Chaetomium spp., Rhizopus spp.) ili četiri meseca (Cladosporium spp.), a treće sporadično u toku tri (Epicoccum spp., Rhizopus spp., Trichothecium spp.), dva (Gliocladium spp.) ili jednog meseca (Papulaspora spp., Phialophora spp.). Period jun-oktobar je najkritičniji za očuvanje kvaliteta uskladištenog kukuruza jer je brojnost (prisutno 8−14 od ukupno 17 identifikovanih rodova gljiva) i frekvencija gljiva u tom periodu najveća, posebno toksigenih vrsta iz rodova Fusarium (43.5−62.5%) i Penicillium (10.0−33.5%). Pozitivna korelacija (r = 0.5979**) između dinamike pojave i frekvencije izolovanih vrsta gljiva ukazuje da se gljive sa većom frekvencijom pojave duže održavaju na zrnu kukuruza tokom skladištenja. F. verticillioides i F. subglutinans su od ukupno šest identifikovanih vrsta roda Fusarium prisutne na zrnu tokom cele godine i sa najvećom frekvencijom (24.7% i 5.9%). U toku jedne godine (2005) F. verticillioides je u najvećem procentu prisutna od februara do oktobra (22.0−39.5%), a F. subglutinans od aprila do oktobra (8.0−12.5%), dok su obe vrste najmanje izolovane u zimskom periodu decembar-januar (4.0−8.0% i 0.5−1.0%). F. graminearum je treća toksigena vrsta roda Fusarium koja sa mikotoksikološkog aspekta može biti značajna za period jun-septembar kada se javlja u najvećem procentu (5.0−11.0%). Pojava ostalih vrsta roda Fusarium je sporadična (1.3% F. proliferatum, 1.0% F. sambucinum and 0.5% F. poae)

Uticaj različitih oblika kalcijum-hidroksida i hlorheksidina kao interseansnih medikamenata na ishod endodontskog lečenja zuba sa hroničnim periapeksnim lezijama

Introduction/Objective The aim of this study was to determine clinical and radiographic periapical healing of teeth with apical periodontitis treated with different formulations of calcium hydroxide (CH) - paste (CH-paste) and gutta-percha points (CH-GP) - as well as those of chlorhexidine (CHX) - gel (CHXgel) and gutta-percha points (CHX-GP) -12 months after therapy. Methods Eighty patients with chronic apical periodontitis were randomly allocated to four treatment groups according to the intracanal medicament used: CH-paste, CH-GP, CHX-gel, and CHX-GP group. Seventy-eight patients were analyzed clinically and radiographically 12 months postoperatively. The periapical index (PAI) was used for the radiographic evaluation of treatment. Results Overall outcome was classified according to radiographic evaluation only, since clinical success was observed in all the patients. In all the groups, significant reduction in PAI scores was observed (p lt 0.001). The proportions of healed teeth (PAI ≤ 2) were 73.7%, 60%, 68.4%, and 65% in CH-paste, CH-GP, CHX-gel and CHX-GP group, respectively, with no significant differences between the groups. Conclusion The results suggest that there are no differences between investigated CH- and CHX-delivery systems regarding treatment outcome of teeth with apical periodontitis.Uvod/Cilj Cilj ovog istraživanja je bio da se ispita klinički i radiografski ishod lečenja zuba sa apeksnim periodontitisom 12 meseci posle završene terapije i primene različitih oblika kalcijum-hidroksida (KH): pasta (KH-pasta) i gutaperka poeni (KH-GP) i hlorheksidina (HH): gel (HH-gel) i gutaperka poeni (HH-GP). Metode Randomizovano je 80 ispitanika sa hroničnim periapeksnim lezijama u četiri grupe na osnovu vrste korišćenog interseansnog medikamenta: KH-pasta, KH-GP, HH-gel i HH-GP. Dvanaest meseci posle završenog lečenja pregledano je 78 ispitanika i urađeni su retroalveolarni snimci. Za procenu radiografskog uspeha lečenja korišćen je periapikalni indeks (PI). Rezultati Ishod lečenja je klasifikovan na osnovu radiološkog nalaza jer je kod svih ispitanika zabeležen klinički uspeh lečenja. U svim ispitivanim grupama je zabeleženo značajno smanjenje vrednosti PI (p lt 0,001). Izlečenje (PI ≤ 2) uočeno je kod 73,3% zuba u grupi KH-pasta, 60% u KH-GP grupi, 68,4% u grupi HH-gel i kod 65% zuba u grupi HH-GP, pri čemu razlike između grupa nisu bile statistički značajne. Zaključak Rezultati ovog istraživanja pokazuju da ne postoji razlika u ishodu lečenja zuba sa apeksnim periodontitisom posle primene ispitivanih oblika KH i HH

Applicability of a Serbian version of the “Oral Impacts on Daily Performance (OIDP)” index - assessment of oral health-related quality of life

Background/Aim. The Oral Impacts on Daily Performance (OIDP) is a well-known psychometric test used internationally to assess the oral health-related quality of life. The interview and self-administrated questionnaire both assess the degree to which oral health problems have affected the life of the participants over the previous 6 months. The aim of this study was to translate the OIDP index into Serbian and to assess its reliability in practice as its initial verification in the Serbian speaking area. Methods. Following an internationally established methods, the OIDP scale was translated using standardized methodology that consisted of forward translation, pilot study and backward translation. Results. A pilot study was carried out with 44 respondents (24 males i 20 females) using a preliminar Serbian version of the OIDP index. All patients were aged over 65 years. A total of 68.2% of the participants replied that they had at least one OIDP impact on daily life in the past 6 months. These troubles were most prominent during eating (47.7%) and speaking (36.4%), but there is a little impact of troubles in the domain of psychosocial sphere. The corrected item-total correlation coefficients for all items were above the minimum recommended level of 0.20 for including an item in a scale. The standardized Cronbach’s alpha coefficient was 0.75. Conclusion. Based on these results, we can conclude that this index is suitable for use in everyday practice in Serbian speaking area providing useful information required to assess oral health-related quality of life

Mechanochemical synthesis of bismuth ferrite

A powder mixture of Bi2O3 and Fe2O3 was mechanically treated in a planetary ball mill in an air from 30 to 720 minutes. It was shown that the mechanochemical formation of BiFeO3 (BFO) phase was initiated after 60 min and its amount increased gradually with increasing milling time. A detailed XRPD structural analysis is realized by Rietveld’s structure refinement method. The resulting lattice parameters, relative phase abundances, crystallite sizes and crystal lattice microstrains were determined as a function of milling time. Microstructural analysis showed a little difference in morphology of obtained powders. The primary particles, irregular in shape and smaller than 400 nm are observed clearly, although they have assembled together to form agglomerates with varying size and morphology. Dense BFO ceramics were prepared by conventional solid-state reaction at the temperature of 810ºC for 1h followed immediately by quenching process. [Projekat Ministarstva nauke Republike Srbije, br. III45007: Zero- to Three-Dimensional Nanostructures for Application in Electronics and Renewable Energy Sources: Synthesis, Characterization and Processin

Application of peach shells for the removal of methylene blue and brilliant green

Increased industrial, agricultural and domestic activities resulted in the production of large amount of wastewater containing a number of toxic materials which continuously polluting the available fresh water. Sorption is an effective method for water decontamination. Various types of pollutants such as metal ions, dyes, and a number of other organic and inorganic compounds and bio-organisms could be removed by different types of sorbents. Important properties of good sorbent material are high specific surface area and fast kinetics for the removal of pollutants. Natural materials such as oil palm fibers and shells, waste apricot and pitch, olive-seeds waste, peach stones, almond shells, walnut shells, hazelnut shells, kaolin, bentonite, zeolites, coal, etc., possess large capacities for removing of the water pollutants. The main advantages of these materials are wide availability, low cost and environmental safety. The peach shells (PS) were used as the raw material for removing of non-degradable toxic dyes from water solutions. Methylene blue (MB) and brilliant green (BG) were used as representatives of dyes which commonly are pollutant from the textile industry. The peach shells were milled in vibromill and sieved to desired sizes: (1) 100-500 μm, and (2) < 100 μm. The phase composition of the prepared particles fractions was identified by XRD. The BET specific surface area was determined from N2 adsorption/desorption experiments. The particles morphology was characterized by SEM, while the particle size distribution was measured by laser light-scattering particle size analyzer. In a typical experiment, 50 mg of PS particles as the sorbent was mixed on a magnetic stirrer with 50 ml of dye aqueous solution with the initial concentration of 5, 10 and 20 ppm, at room temperature. At time intervals of 5 to 120 minutes aliquots was withdrawn, centrifuged, and pollutant concentration was measured. The concentration of MB and BG in the solution before and after sorption by PS was calculated according to the absorbance value at 665 nm (for MB) and 624 nm (for BG) determined by UV measurements performed on a UV–Vis spectrophotometer in the wavelength range of 300–800 nm. Capacity of MB and BG sorption by prepared PS particles was found to be above 86 % after 120 minutes

Comparative study of the effects of different nanomaterials on the viability of human osteoblast-like cells

The aim of this study was to compare the effects of two types of nanomaterials, cobalt-exchanged hydroxyapatite (CoHAp) and calcium phosphate/poly-(DL-lactide-co-glycolide) (CP/PLGA), on the viability of Saos-2 osteoblast-like cells, using MTT test. We have examined the suspension of this materials in the following concentrations: 1.6, 8, 40, 200, 1000 and 2500 μg/ml, as well as extracts in concentration range from 2,5% to 100%. Both materials showed cytotoxic effect at higher concentrations of suspension and extract, respectively, but they were not cytotoxic at lower concentrations. CP/PLGA acted stronger cytotoxic compared to CoHAp, regardless of whether it is examined suspension or extract. CoHAp in small concentrations of suspension and extract acted slightly stimulatory on cells. This suggests that CoHAp may have advantage for use in the in vivo systems

Enhancing the customer relationship management in public libraries: findings from three developing countries

Purpose – The purpose of this paper is to investigate the possibilities of implementing the customer relationship management (CRM) concept and smart technologies in public libraries in developing countries. The goal was to explore the level of librarians’ awareness about CRM concept and their willingness to accept the CRM concept in libraries. Also, patrons’ satisfaction with the quality of services and relationships in public libraries is explored. Design/methodology/approach – The authors obtained data for this research through two online surveys. The first survey measures librarians’ level of awareness about CRM concept and their perception about CRM and smart technologies concept in public libraries in three developing countries: Serbia, Montenegro and Bosnia and Herzegovina. The second survey measures patrons’ satisfaction with services and relationship in public libraries in these three countries. Findings – The research results revealed that most surveyed librarians are familiar with the CRM concept. However, libraries in these three developing countries barely use CRM or smart technologies to improve the relationship with stakeholders. Also, most patrons are satisfied with relationships and services. The analysis of data indicates no significant difference in the satisfaction level among patrons between these three developing countries. Research limitations/implications – Not all libraries participated in this research. Therefore, the sample is not distributed evenly across different types of libraries or user groups. Future research should include different types of libraries. Practical implications – The results can be used by public libraries in developing countries to improve the relationship with stakeholders harnessing CRM concept and smart technologies. Social implications – The use of CRM in combination with the smart technologies can help leverage the quality of the relationship between public libraries and stakeholders which in turn would secure their support and loyalty in the future. Originality/value – The integration of CRM concept as a component of library business automation process is an idea that has not been discussed widely in the library community and could initiate a positive trend in public libraries in developing countrie

Upotreba mobilnih tehnologija u srednjoškolskom obrazovanju

Cilj ovog rada je analiza načina i preferencija upotrebe mobilnih tehnologija i, u okviru njih, posebno, društvenih mreža, za potrebe obrazovanja među srednjoškolskom populacijom u Srbiji. U okviru rada predstavljeno je istraživanje sprovedeno u aprilu 2016. godine, o u potrebi mobilnih tehnologija od strane učenika Pete ekonomske škole iz Beograda. Dobijeni rezultati pokazali su da trendovi korišćenja informacionih tehnologija u domaćim srednjim školama na približno istom nivou kao i u sličnim istraživanjima sprovedenim u drugim državama. Takođe, rezultati istraživanja pokazuju i da postoji prostor za unapređenje primene savremenih informacionih tehnologija u procesu obrazovanja