Genotoxic Potential of Dentin Bonding Agents

Svrha rada bila je ispitati genotoksično djelovanje pet dentinskih adheziva: Adper Single Bonda, Adper Single Bonda 2, Prompt L-popa, Excitea i OptiBonda Solo Plus. Ispitivanje genotoksičnosti provedeno je na humanim limfocitima periferne krvi u uvjetima in vitro, ispitane koncentracije adheziva bile su 0,2, 0,5 i 5 μg/ml, a testirana vremena eluacije 1 sat, 24 sata i 5 dana. Genotoksičnost adheziva ispitivala se citogenetičkom metodom - analizom strukturnih aberacija kromosoma, dakle, određivanjem ukupnog broja kromosomskih lomova, kromatidnih lomova i acentričnih fragmenata. Rezultati pokazuju genotoksičnost OptiBonda Solo Plus već u koncentraciji 0,2 μg/ml i to nakon 24-satne eluacije, zatim OptiBonda Solo Plus u koncentraciji 0,5 μg/ml nakon jednosatne eluacije, OptiBonda Solo Plus, Adper Single Bonda 2 i Excitea u koncentraciji 0,5 μg/ml nakon jednodnevne eluacije. U koncentraciji 5 μg/ml nakon jednosatne eluacije genotoksičnost su pokazali OptiBond Solo Plus, Excite, Adper Single Bond 2 i Adper Single Bond, a nakon jednodnevne eluacije svi su ispitivani adhezivi pokazali genotoksičnost. Iz rezultata je jasno da enotoksičnost raste s porastom koncentracije adheziva, a smanjuje se s vremenom. Najveća genotoksičnost zabilježena je nakon 24-satne eluacije.The aim of this study was to examine the genotoxic activity of five dentin bonding agents: Adper Single Bond, Adper Single Bond 2, Prompt L-pop, Excite and Opti-Bond Solo Plus. This in vitro study was performed on human lymphocytes from peripheral blood, and the concentrations of dentin bonding agents tested were 0.2, 0.5 i 5 μg/ml, and elution times tested were 1 hour, 24 hours and 5 days. Genotoxicity testing was done using the Structural chromosomal aberration analysis cytogenic method , which determined the complete number of chromosome breaks, chromatide breaks and acentric fragments. The results showed genotoxicity of Opti-Bond Solo Plus in the 0.2 μg/ml concentration after a 24-hour elution period, then OptiBond Solo Plus in the 0.5 μg/ml concentration after a 1 hour elution period and OptiBond Solo Plus, Adper Single Bond 2 and Excite in the 0.5 μg/ml concentration after a 1 day elution period. In the 5 μg/ml concentration after 1 hour of elution, genotoxic potential was observed in cultures with OptiBond Solo Plus, Excite, Adper Single Bond 2 and Adper Single Bond, while all dentin bonding agents showed genotoxicity at that highest concentration but after 1 day of elution. From the results it is obvious that genotoxicity increases with the concentration of the dentin bonding agent, and decreases over time. The highest genotoxicity was observed after a 24-hour-elution period

Multi-fluid model predictions of gas-liquid two-phase flows in vertical tubes

Razvijen je potpun, stabilan, jednodimenzioni višefluidni model za predviđanje dvofaznog strujanja u vertikalnim cevima. Model je zasnovan na bilansima održanja mase, količine kretanja i energije, koji su primenjeni na svaku fluidnu struju koja je prisutna u posmatranom obliku dvofaznog strujanja, kao i na odgovarajućim konstitutivnim korelacijama za određivanje transportnih procesa na razdelnim površinama između faza. Bilansne jednačine za stacionarno stanje su transformisane u oblik pogodan za direktnu primenu numeričke metode za integraciju sistema običnih diferencijalnih jednačina. Simulirani su termohidraulički procesi duž celog isparivačkog kanala, počevši od strujanja i zagrevanja pothlađene tečnosti na ulazu u strujni kanal pa do zasušenja tečnog filma i pojave maglenog toka sa kapima uključenim u gasnu fazu na kraju kanala. Takođe, model je testiran i za uslove nekoliko parcijalnih efekata dvofaznog strujanja.A consistent one-dimensional multi-fluid model is developed for the prediction of two-phase flows in vertical pipes. The model is based on the mass, momentum and energy balance equations for every fluid stream involved in the observed two-phase flow pattern, and corresponding closure laws for interface transfer processes. The steady-state balance equations are transformed in a form suitable for a direct application of the numerical integration method for the system of ordinary differential equations. Thermal-hydraulic processes along the whole length of the boiling channel are simulated, from the flow and heating of sub cooled liquid at the flow channel inlet, and up to the liquid film dry out and gas entrained droplets mist flow at the outlet. Also, the model is tested against several partial effects of two-phase flow

Numerical simulation of condensation induced water hammer

Razvijen je numerički model za simulaciju i analizu hidrauličkog udara koji je zasnovan na jednodimenzionalnom homogenom modelu dvofaznog strujanja praćenju razdelne površine stuba tečnosti i parnog mehura i modeliranju direktne kondenzacije pare na pothlađenoj tečnosti. Sistem bilansnih jednačina je rešen primenom metode karakteristika. Integracija je vršena duž tri karakteristična pravca: dva pravca određena su pravcem prostiranja talasa pritiska a treći prostiranjem fluidnog delića. Praćenje fluidnog delića i razdelne površine vode i pare izvršeno je rešavanjem energetske jednačine u prostoru sa tačnošću trećeg reda. Količina toplote koju para preda tečnosti pri kondenzaciji određena je integracijom površinskog toplotnog fluksa po razdelnoj površini parne i tečne faze na mestu kontakta pare i pothlađene tečnosti. Model je primenjen na simulaciju i analizu hidrauličkog udara izazvanog u nekoliko eksperimentalih aparatura.A numerical model for the simulation and analysis of the water hammer in the pipe two-phase flow is developed. The modeling is based on one-dimensional homogeneous model of two-phase flow, tracking of the interface between steam volume and water column and modeling of the direct condensation of steam on sub cooled liquid. The mass, momentum and energy conservation equations are solved by the method of characteristics. For these three equations, there are three characteristic directions: two of them are determined by the pressure wave propagation and the third one by the fluid particle propagation. The fluid particle and the steam-water interface tracking are obtained through the energy conservation equation solving in space, with the accuracy of the third degree. The value of thermodynamic quality is used to determine whether the observed computational region is filled with water, two-phase mixture or steam. The term in the energy conservation equation, which contains information about the heat exchanged between steam and liquid phase through condensation, is determined by integration of superficial heat flux over steam-water interface. The model is applied to the simulation and analysis of the air-water interface propagation in the experimental apparatus of oscillating manometer and the condensation induced water hammer in a vertical pipe for draining of steam into the pool filled with sub cooled water

Numerical simulation of condensation induced water hammer

Razvijen je numerički model za simulaciju i analizu hidrauličkog udara koji je zasnovan na jednodimenzionalnom homogenom modelu dvofaznog strujanja praćenju razdelne površine stuba tečnosti i parnog mehura i modeliranju direktne kondenzacije pare na pothlađenoj tečnosti. Sistem bilansnih jednačina je rešen primenom metode karakteristika. Integracija je vršena duž tri karakteristična pravca: dva pravca određena su pravcem prostiranja talasa pritiska a treći prostiranjem fluidnog delića. Praćenje fluidnog delića i razdelne površine vode i pare izvršeno je rešavanjem energetske jednačine u prostoru sa tačnošću trećeg reda. Količina toplote koju para preda tečnosti pri kondenzaciji određena je integracijom površinskog toplotnog fluksa po razdelnoj površini parne i tečne faze na mestu kontakta pare i pothlađene tečnosti. Model je primenjen na simulaciju i analizu hidrauličkog udara izazvanog u nekoliko eksperimentalih aparatura.A numerical model for the simulation and analysis of the water hammer in the pipe two-phase flow is developed. The modeling is based on one-dimensional homogeneous model of two-phase flow, tracking of the interface between steam volume and water column and modeling of the direct condensation of steam on sub cooled liquid. The mass, momentum and energy conservation equations are solved by the method of characteristics. For these three equations, there are three characteristic directions: two of them are determined by the pressure wave propagation and the third one by the fluid particle propagation. The fluid particle and the steam-water interface tracking are obtained through the energy conservation equation solving in space, with the accuracy of the third degree. The value of thermodynamic quality is used to determine whether the observed computational region is filled with water, two-phase mixture or steam. The term in the energy conservation equation, which contains information about the heat exchanged between steam and liquid phase through condensation, is determined by integration of superficial heat flux over steam-water interface. The model is applied to the simulation and analysis of the air-water interface propagation in the experimental apparatus of oscillating manometer and the condensation induced water hammer in a vertical pipe for draining of steam into the pool filled with sub cooled water

Multi-fluid model predictions of gas-liquid two-phase flows in vertical tubes

Razvijen je potpun, stabilan, jednodimenzioni višefluidni model za predviđanje dvofaznog strujanja u vertikalnim cevima. Model je zasnovan na bilansima održanja mase, količine kretanja i energije, koji su primenjeni na svaku fluidnu struju koja je prisutna u posmatranom obliku dvofaznog strujanja, kao i na odgovarajućim konstitutivnim korelacijama za određivanje transportnih procesa na razdelnim površinama između faza. Bilansne jednačine za stacionarno stanje su transformisane u oblik pogodan za direktnu primenu numeričke metode za integraciju sistema običnih diferencijalnih jednačina. Simulirani su termohidraulički procesi duž celog isparivačkog kanala, počevši od strujanja i zagrevanja pothlađene tečnosti na ulazu u strujni kanal pa do zasušenja tečnog filma i pojave maglenog toka sa kapima uključenim u gasnu fazu na kraju kanala. Takođe, model je testiran i za uslove nekoliko parcijalnih efekata dvofaznog strujanja.A consistent one-dimensional multi-fluid model is developed for the prediction of two-phase flows in vertical pipes. The model is based on the mass, momentum and energy balance equations for every fluid stream involved in the observed two-phase flow pattern, and corresponding closure laws for interface transfer processes. The steady-state balance equations are transformed in a form suitable for a direct application of the numerical integration method for the system of ordinary differential equations. Thermal-hydraulic processes along the whole length of the boiling channel are simulated, from the flow and heating of sub cooled liquid at the flow channel inlet, and up to the liquid film dry out and gas entrained droplets mist flow at the outlet. Also, the model is tested against several partial effects of two-phase flow

Adsorption kinetics and mechanism analysis of cyan printing dye on polyethylene microplastics

Printing on polymer materials might result with generation of coloured wastewater, enriched with a certain amount of microplastics in a form of polyethylene or polypropylene. In that way, microplastics may acquire the function of carriers of synthetic dyes, heavy metals and other polluting substances. In this paper, kinetics and adsorption mechanism of printing Cyan dye on polyethylene (powdered and granulated), as one of the most common types of microplastics, were investigated. The experiments were performed in a batch mode, in laboratory conditions. Based on the obtained results, a similar adsorption rate degree of selected printing dye was determined on granulated (adsorbed amount was 48.04 µg/g) and powdered material (adsorbed amount was 44.32 µg/g). The adsorption data were fitted well by pseudo-second-order kinetics, while isotherm studies were evaluated using two models: Langmuir and Freundlich. Freundlich and Langmuir equations showed similar performances to fit the solid/liquid distribution of Cyan dye on powdered polyethylene (R2 = 0.987), whereas Langmuir equation showed slightly better performances for granulated polyethylene than Freundlich equation

Zastupljenost oganohlornih pesticida u filetima oslića

Organohlorni pesticidi (OCP) su grupa jedinjenja široko zastupljena u prirodi a samim tim i u hrani koju konzumiramo. Da bismo za proizvod rekli da je bezbedan za upotrebu neophodno je da sadržaj OCP-a u njemu bude manji od maksimalno dozvoljenih vrednosti koje su propisane važećim Pravilnikom. Identifikacija ove grupe jedinjenja se vrši gasnom hromatografijom sa masenim detektorom. Priprema uzoraka za analizu sa brzom QuECHERS metodom obezbeđuje da za kratko vreme, pouzdano ekstrahujemo analite od interesa. U našoj studiji ispitivali smo sadžaj 19 organohlornih pesticida u filetima oslića, ribljem proizvodu popularnom u našoj zemlji. Ispitivanja su pokazala da se koncentracija OCP-ova u ovim proizvodima nalazi znatno ispod maksimalno dozvoljenih koncentracija. Organohlorni pesticidi se akumuliraju u hrani i okruženju što izaziva zabrinutost zbog potencijalnih rizika po ljudsko zdravlje kao i zbog narušavanja ekološke ravnoteže (Kartalovic et al, 2015). U predhodnim decenijama organohlorni pesticidi su se koristili širom sveta kako bi unapredili poljoprivrednu proizvodnju. Globalna upotreba ove grupe jedinjenja je od 1950. godine dovela je do povećanja njihove potrošnje i do pedeset puta, paralelno sa rastom stanovništva (Nath, 2013). U našoj studiji ispitivali smo slučajno izabrane uzorke iz marketa. Uzorci su do ispitivanja čuvani u orginalnom pakovanju u skladu sa preporukom proizvođača. Na osnovu ispitivanja 18 uzoraka zaključeno je da je sadržaj organohlornih pesticida znatno niži od maksimalno dozvoljenih koncentracija u ribi, koje su propisane važećim Pravilnikom Republike Srbije. Opseg koncentracija OCP-a se kretao od 0.0065-0.0097 mg/kg. Generalno, svi pesticidi su toksične supstance dizajnirane da ubiju štetočine sa svojim otrovnim ili štetnim efektima. Direktno ili indirektno pesticidi mogu ući u ljudsko telo kroz lanac ishrane i konačno, mogu prouzrokovati različite efekte na ljudsko zdravlje, poput alergijskih reakcija uključujući i sterilitet i kancer. Zagađivanje hrane sa ovim supstancama se smatra jednim od najopasnijih aspekata u poslednjih nekoliko godina. Riba i riblji proizvodi mogu biti kontaminirani sa hloriovanim ostacima kroz različite izvore. Ovi kvaliteti ih čine najopasnijom grupom hemikalija kojima prirodni sistemi mogu biti izloženi i funkcionišu kao hemijski indikatori antropogenog pritiska i zagađenja (Baiarri i dr., 2001; Storelli et al.,2004). Zbog činjenice da su OCP ipak prisutni u ovim proizodima neophodno je iste izloziti stalnom monitoringu s ciljem obezbeđivanja plasmana samo bezbednih proizvoda na naše trzište

Numerical simulation of dynamic loads at the steam pipe line of the thermal power plant 'Nikola Tesla B”

Određivanje dinamičkih sila kojima nestacionarna struja fluida deluje na cevovod je neophodno u cilju sagledavanja maksimalnih naprezanja koja deluju na strukturu, spojeve i oslonce, odnosno u cilju dobijanja podloga za projektovanje ovih elemenata na maksimalna dinamička naprezanja. U radu su prikazani metodologija i rezultati računarske simulacije nestacionarnih gasodinamičkih sila koje deluju na parovod tople međupregrejane pare termoelektrane „Nikola Tesla B”. Nestacionarne gasodinamičke sile nastaju usled nestacionarnog strujanja radnog fluida pri delovanju sigurnosno-zaštitnih sistema. Zatvaranje pregradnih ventila ispred tur bine srednjeg pritiska zaustavlja protok pare i dovodi do porasta pritiska ispred pregradnih ventila, i prostiranja i superponiranja talasa pritiska duž parovoda, što izaziva dopunska dinamička opterećenja parovoda. Određivanje dinamičkih fluidnih sila se vrši zajedno sa simulacijom nestacionarnog strujanja pare. Simulacija strujanja i određivanje fluidnih dinamičkih sila su sprovedeni pomoću računarskog programa TEA razvijenog na Mašinskom fakultetu u Beogradu. Dobijeni rezultati su korišćeni u okviru revizije inostranog projekta rekonstrukcije (zamene) parovoda međupregrejane pare na termoelektrani „Nikola Tesla B”. Rezultati proračuna dobijeni programom TEA su upoređeni sa rezultatima inostranog računarskog programa SHOCK i dobijeno je prihvatljivo slaganje.Prediction of the transient fluid dynamic forces that act on the pipe line structure, junctions and supports are important in order to predict the maximum design loads. The paper presents the methodology and results of the fluid dynamic forces prediction for the reheated steam pipe line at the Thermal Power Plant ”Nikola Tesla B”. The dynamic forces are induced by fluid transient flow caused by the action of the plant safety system. Closure of the isolation valves in front of the intermediate pressure turbine stops the steam flow and leads to the in crease of pres sure in front of the isolation valves, pressure waves propagation and super position along the pipe line, which cause additional dynamic loading of the pipe line structure. Prediction of the fluid dynamic forces is performed simultaneously with the simulation of the transient fluid flow. Transient simulation of fluid flow and calculation of fluid-dynamic forces are performed with the computer code TEA (Transient Evaluation Analyses), which is developed at the Faculty of Mechanical Engineering in Belgrade. Obtained results are used for the review of a foreign project on the reconstruction (replacement) of steam pipeline in Thermal Power Plant ”Nikola Tesla B”. Results obtained with the computer code TEA are compared with results of foreign computer code SHOCK. Acceptably agreement is achieved

Numerical simulation of dynamic loads at the steam pipe line of the thermal power plant 'Nikola Tesla B”

Određivanje dinamičkih sila kojima nestacionarna struja fluida deluje na cevovod je neophodno u cilju sagledavanja maksimalnih naprezanja koja deluju na strukturu, spojeve i oslonce, odnosno u cilju dobijanja podloga za projektovanje ovih elemenata na maksimalna dinamička naprezanja. U radu su prikazani metodologija i rezultati računarske simulacije nestacionarnih gasodinamičkih sila koje deluju na parovod tople međupregrejane pare termoelektrane „Nikola Tesla B”. Nestacionarne gasodinamičke sile nastaju usled nestacionarnog strujanja radnog fluida pri delovanju sigurnosno-zaštitnih sistema. Zatvaranje pregradnih ventila ispred tur bine srednjeg pritiska zaustavlja protok pare i dovodi do porasta pritiska ispred pregradnih ventila, i prostiranja i superponiranja talasa pritiska duž parovoda, što izaziva dopunska dinamička opterećenja parovoda. Određivanje dinamičkih fluidnih sila se vrši zajedno sa simulacijom nestacionarnog strujanja pare. Simulacija strujanja i određivanje fluidnih dinamičkih sila su sprovedeni pomoću računarskog programa TEA razvijenog na Mašinskom fakultetu u Beogradu. Dobijeni rezultati su korišćeni u okviru revizije inostranog projekta rekonstrukcije (zamene) parovoda međupregrejane pare na termoelektrani „Nikola Tesla B”. Rezultati proračuna dobijeni programom TEA su upoređeni sa rezultatima inostranog računarskog programa SHOCK i dobijeno je prihvatljivo slaganje.Prediction of the transient fluid dynamic forces that act on the pipe line structure, junctions and supports are important in order to predict the maximum design loads. The paper presents the methodology and results of the fluid dynamic forces prediction for the reheated steam pipe line at the Thermal Power Plant ”Nikola Tesla B”. The dynamic forces are induced by fluid transient flow caused by the action of the plant safety system. Closure of the isolation valves in front of the intermediate pressure turbine stops the steam flow and leads to the in crease of pres sure in front of the isolation valves, pressure waves propagation and super position along the pipe line, which cause additional dynamic loading of the pipe line structure. Prediction of the fluid dynamic forces is performed simultaneously with the simulation of the transient fluid flow. Transient simulation of fluid flow and calculation of fluid-dynamic forces are performed with the computer code TEA (Transient Evaluation Analyses), which is developed at the Faculty of Mechanical Engineering in Belgrade. Obtained results are used for the review of a foreign project on the reconstruction (replacement) of steam pipeline in Thermal Power Plant ”Nikola Tesla B”. Results obtained with the computer code TEA are compared with results of foreign computer code SHOCK. Acceptably agreement is achieved

Experimental design of photo-Fenton process decolorization of Reactive Red 120 by using mathematical statistics models

A statistical design of experiments was used to evaluate the potential use of clay catalyst (CuOFeB) during photo-Fenton process in which the concentration of hydrogen peroxide (H2O2), catalyst loading and pH values were selected as effective experimental factors in the process of dye decolorization. The photo-Fenton oxidation of Reactive Red 120 (RR120) has been investigated using a concentrating solar parabolic reactor with constant solar radiation of 950 W/m2 during summer period of the year. Under the optimal reaction conditions catalyst showed good catalytic activity in the processes with dye removal over 90%. Also, experiment confirmed that decolorization efficiency depends on the pH and concentration of H2O2 , wherein better results were achieved under lower pH values and higher concentration of H2O2