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Bioactive Hydroxyapatite/Chitosan/Gentamicin Composite Coating Electrodeposited on Titanium
No full textTitanium (Ti) is the most widely used implant material due to its high corrosion
resistance, and good mechanical properties. The biocompatibility and bioactivity of
titanium can be significantly improved by the modification of its surface through the
deposition of bioceramic coating on Ti [1]. Materials of choice were hydroxyapatite
(HAP), chitosan (CS) and gentamicin because of their good properties. HAP is well
known for its outstanding biocompatibility, chemical composition similar to natural
bone and its ability to promote osseointegration. Improvement of mechanical and
antimicrobial properties of the coating was achieved by addition of CS, biocompatible,
natural polymer [2]. In order to improve antibacterial properties, and to avoid
the occurrence of various inflammatory processes during implantation, a broad
spectrum antibiotic gentamicin was added [3]. The combination of good mechanical
properties of Ti, the bioactivity of HAP and good adhesion properties of CS enables
the production of bone tissue implants with improved biological functions.
Cathodic electrophoretic deposition process (EPD) was employed for assembling
composite HAP/CS and HAP/CS/Gent coating on Ti substrate (Figure 1.). EPD was
carried out at the constant voltage on pure Ti plates from an aqueous suspension.
The aim was to produce homogenous bioactive coatings with improved mechanical
properties and remarkable antibacterial effects. Obtained coatings were characterized
by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM).
Antibacterial properties of coatings were tested against two bacteria strains – Staphylococcus
aureus and Escherichia coli, by agar diffusion test. Evaluation of relative
cytotoxicity of obtained coatings was performed using MTT test. The ability of
coatings to promote osseointegration was tested using ALP assay.
Obtained results confirmed the successful deposition of HAP/CS and HAP/CS/Gent
coatings on Ti using EPD technique. Hydrogen bonding of functional groups of
CS and HAP was confirmed by FT-IR analysis which also revealed several bands
characteristic for CS. Due to low gentamicin content in HAP/CS/Gent coating, no
characteristic bands corresponding to gentamicin were detected. The presence of
gentamicin in HAP/CS/Gent was revealed by XPS analysis through the deconvolution
of C1s peak that indicated binding of gentamicin to the matrix. Addition of the
polymer significantly improved morphology, and bioactivity of thus formed
composite. Morphology examination of HAP/CS and HAP/CS/Gent is represented
in Figure 2. FE-SEM micrographs confirmed bioactivity of HAP/CS and HAP/CS/
Gent after immersion in SBF. The rapid formation of apatite in a relatively short time
(after only 7 days) showed coatings ability to promote bonding between natural bone
and implants. MTT assay for HAP/CS and HAP/CS/Gent indicated low cytotoxicity
against MRC-5 and L929 cell lines. Both composite coatings exhibited strong
antibacterial activity against S.aureus and E. coli, indicating the high potential for
biomedical applications. This effect was slightly more pronounced for the samples
tested against S. aureus, for both HAP/CS and HAP/CS/Gent coatings.
Excellent osteogenic properties, through the promotion of osteoblast differentiation
were confirmed by ALP assay. Results were much more pronounced for HAP/CS/
Gent coating. Therefore, HAP/CS and HAP/CS/Gent coatings can be considered as
an excellent promising candidate for biomedical hard tissue implants [4]
Tektonotermalna evolucija asimetričnog ekstenzionog sistema: planina Juhor (severni deo Srpsko‐makedonskog masiva)
No full textСавремена проучавања тектонских односа у Панонском басену се заснивају на наглашеној
унутрашњој деформисаности главних тектонских јединица којe изграђују основу басена, наспрам
схватања да се кретања дешавају дуж обода ригидних блокова. Јухор се налази у централној
Србији и представља усамљену планину коју граде протерозојски до палеозојски метаморфити
амфиболске фације. На падинама и у непосредном окружењу Јухора се налазе миоценски до
квартарни седименти јужног обода Панонског басена. Јухор, заједно са осталим издигнутим
пределима у Моравском рову, као што су Црни Врх, Мојсињске и Послонске планине, чине се‐
верни део Српско‐македонског масива. Српско‐македонски масив се одликује средње до високо
метаморфисаним фацијама представљеним гнајсевима, дволискунским шкриљцима и амфиболи‐
тима (Dimitrijević, 1997). Ова тектонска јединица се може корелисати са јединицом Бихарија,
заједно чинећи структурно највише делове Дакијске јединице која се одликује Европским тек‐
тонским афинитетом (Matenco and Radivojević, 2012). Новија термохронолошка истраживања на
југоистоку Србије и у околини указују да се врхунац метаморфизма у Српско‐македонском масиву
одиграо током варисцинског циклуса док је током целог палеозоика долазило до магматске
активности (Antić et al., 2016a). Јужно од истраживаног простора, везана кинематска и термохро‐
нолошка истраживања на планини Јастребац, указују да је касно кредни екстензиони детачмент
раздвојио високометаморфисане стене Српско‐македонског масива у подини од слабије метамор‐
фисаних стена Супрагетикума у повлати (Erak et al., 2016). Ова врста и старост деформација су у
новије време описане у суседним областима, по ободу Динарида, које се налазе у сличним
тектонским условима. Ови догађаји су везани за екстензију које је захватила fore‐arc подлогу
током субдукције Неотетиса крајем креде (Antić et al., 2016b; Toljić et al., 2018). Теренским
осматрањима се уочавају упадљиве морфолошке, структурне и литостратиграфске разлике између
метаморфита Јухорa и околних миоценских до квартарних наслага. Ово указује да су каснији де‐
формациони догађаји који су захватили северне делове Српско‐македонског масива везани за
формирање и развој југоисточног обода Панонског басена. Остаје доста непознатих чињеница о
прецизнијем временском оквиру и износима тектонског издизања Јухора. У циљу одређивања
износа ексхумације у северним деловима Српско‐македонског масива, спроведена су кинематска
и термохронолошка испитивања. Прелиминарни резултати термохронолошких испитивања, тра‐
гова фисије (AFT) и хелијума (AHe) у апатитима, указују на миоценски интервал хлађења метамор‐
фита на Јухору што се може довести у везу са екстензионом реактивацијом контакта Српско‐ма‐
кедонског масива и Супрагетикума током миоцена. Реактивација се догодила дуж екстензионог
детачмента у чијој подини се налазе метаморфити Јухора док је у повлати дошло до таложења
доње до средње миоценских наслага у Моравској депресији (Моравски детачмент према Sant et
252
al., 2016). Накнадна плиоценско‐квартарна инверзија Панонског басена је довела до даљег
обликовања релативно издигнутих и спуштених тектонских блокова дуж јужног обода басена.Studies on recent tectonic setting of the Pannonian Basin argue for the internal deformation of
principal tectonic units constituting the basement of the basin, rather than motion along the boundaries
of large‐scale fully rigid blocks (Bada et al., 2007). The Juhor Mts in central Serbia represent an inselberg
of Proterozoic to Paleozoic age amphibolite‐facies metamorphics surrounded by Miocene to Quaternary
sediments of the southernmost Pannonian Basin. The Juhor Mts, together with other uplifted areas
along the Morava river corridor, such as Crni Vrh, Mojsinjske Mts, Poslonske Mts, comprise part of
northern Serbomacedonian Massif. The Serbomacedonian Massif is characterized by a medium to
high‐degree metamorphic sequence comprised of gneisses, two‐mica schists and amphibolites (e.g. Dimitrijević,
1997). This unit can be correlated with the Biharia nappe, together defining structurally
highest parts of the European‐derived Dacia mega‐unit (Matenco and Radivojević, 2012). Recent
thermochronological studies in the SE Serbia and adjacent countries have inferred that the peak
metamorphic event in the Serbomacedonian unit is Variscan and that its magmatism had a long
Paleozoic evolution (Antić et al., 2016a). South of our study area, a coupled kinematic and thermochronological
study conducted in the Jastrebac Mts has inferred a Late Cretaceous extensional detachment
creating the separation between the high‐grade metamorphics of the Serbomacedonian unit
in the footwall and the weakly metamorphic Supragetic nappe in the hanging‐wall (Erak et al., 2016).
This type and age of deformation was recently described in other neighbouring areas situated in similar
tectonic positions along the Dinaridic strike and are related to the extension recorded in the fore‐arc
basement during the Late Cretaceous subduction of the Neotethys Ocean (see also Antić et al., 2016b;
Toljić et al., 2018). Field observations show striking morphological, structural, and litho‐stratigraphic
contrast between the Juhor metamorphics and the adjacent Miocene to Quaternary deposits. Hence,
the observed omission could infer that the later stages of deformation in the northern Serbomacedonian
Massif were directly related to formation and evolution of the southeastern Pannonian Basin.
However, not much is known about the actual timing and amounts of the mountains tectonic uplift. In
order to quantify the recent stages of exhumation in the northern Serbomacedonian Massif we
conducted a coupled kinematic and thermochronological study. Preliminary results of our AFT and AHe
thermochronological study yield Miocene age cooling in the Juhor metamophites, thus inferring Miocene
extensional reactivation of the Serbomacedonian and Supragetic nappes contact. This reactivation
occurred along extensional detachment, whereby Juhor metamorphites represent exhumed footwall
while the hanging wall accommodated Lower to Middle Miocene deposition of the Morava depression
(the Morava detachment, see Sant et al., 2016). Subsequent Pliocene to Quaternary inversion of the
Pannonian Basin resulted in further differentiation between uplifted and subsided tectonic blocks along
southern margin of the basin
Hidročađi kao potencijalni adsorbensi različitih polutanata iz otpadnih voda
No full textHidrotermalna karbonizacija (HTC) predstavlja tehnološki unapređenu tehnologiju za konverziju otpadne biomase u proizvode različite upotrebne vrednosti. Prednost ovog postupka jeste upotreba biomase sa visokim sadržajem vlage bez potrebe za sušenjem, te se HTC može primeniti na brojne prekursore za dobijanje hidročađi. Zahvaljujući svom strukturnom sastavu hidročađi pokazuju veliki potencijal za uklanjanje različitih polutanata iz vodenih rastvora. Adsorpcione karakteristike hidročađi u velikoj meri zavise od uslova proizvodnje i polazne sirovine. Ovaj rad se fokusira na pregled najnovijih studija primene hidročađi dobijene HTC postupkom za tretman otpadnih voda, a u cilju promovisanja ove napredne tehnologije za preradu otpadne biomase u efikasne adsorbense
Uticaj smanjenja sadržaja metala u ulaznoj rudi na vrednost Bondovog radnog indexa Pb-Zn rude iz rudnika “Grot”-Kriva Feja -Vranje
No full text„Rudnik Pb-Zn Grot“-Kriva Feja-Vranje, bavi se eksploatacijom Pb-Zn rude, od 1974. godine. Tehnološka šema postupka pripreme i koncentracije rude je osmišljena i definisana posle detaljnih ispitivanja obavljenih na Rudarsko-geološkom fakultetu u Beogradu i Rudarskom Institutu Zemun. Prema Glavnom Tehnološkom projektu koncentracija rude iz 1970. godine postrojenje za preradu je projektovano za sledeće polazne parametre:
- celokupno postrojenje za preradu Pb-Zn rude je projektovano za kapacitet od 300.000 t/god. (Glavni Tehnološko-mašinski projekat – Projekni zadatak Knjiga I list 1).
- sadržaja korisnih metala u obliku sulfida u ulaznoj rudi Pb + Zn je zbirno oko 10%,
- separacija sulfidnih minerala Pb i Zn u zasebne proizvode se izvodi postupkom flotacijske koncentracije
- sadržaj vlage (vode) u ulaznoj rudi je od 3,5%
Tokom vremena eksploatacije koja traje duže od četrdeset godina polazni parametri rude su se dosta izmenili, pre svega polazna ruda koja se sada eksploatiše je sa daleko manjim sadržajem metaličnih minerala zbirno (Pb+Zn) oko i ispod 5%. U rudi su prisutni pored sulfidnih i oksidni minerali Pb i Zn itd.
Pored toga što je zbirni srednji sadržaj metala u ulaznoj rudi pao ispod 5% (Tabele 1., 2.), u odnosu na projektovane vrednosti (zbirno Pb+Zn oko 10%), iz tih razloga izmenjen je i Bondov radni index rude, kao i njena tvrdoća i meljivost. Izmena karakteristika rude dovodi neminovno i do promene svih radnih parametara svih uređaja za usitnjavanje (habanja radnih delova, promene normativnih troškova čelika, promene potrošnje energije). U sadašnjem momentu ulazna krupnoća rude u mlin sa šipkama je preko 60 (80) mm, a i ruda je izmenjena u odnosu projektni zadatak, odnosno postoje komadi rude veličine od 60 mm pa i više koji prođu kroz mlin i ne samelju se, što je konstatovano obilaskom samog postrojenja, da je ruda na ulazu u mlin sa kuglama daleko krupnija nego što je to predviđeno projektom.
Projektom je predviđeno da izlazna krupnoću usitnjene rude (posle drobljenja) bude 30-40 mm (u Glavnom tehnološkom-mašinskom projektu kao izlazne krupnoće usitnjene rude figuriraju sledeće krupnoće 25, 30 i 40 mm, Glavni Tehnološko-mašinski projekat Sveska I listovi 4, 5 i 6, kao i u Aneksu I list 1, 11 i 12- 25 mm, zatim u Svesci I listovi 15 i 34-javlja se i 30 mm, dok u šemi kretanja masa i pri proračunu mlina sa šipkama Sveska I list 66 figurira ggk ulazne rude 40mm), a u praksi je to 60 pa i više milimetara.
Osim ovih vizuelnih pokazatelja uočeno je da je u nekoliko poslednjih godina porasla potrošnja električne energije u preradi rude sa 34 na 39-40 kWh/t. Iz svih ovih razloga predloženo je rukovodiocima rudnika da se izvrši određivanje Bondovog radnog indexa na reprezentativnom uzorku rude
Principi održivog razvoja kao direktni faktori u zaštiti životne sredine
No full textEksploatacija mineralnih sirovina i razvoj novih materijala nameću pitanje kako sačuvati životnu sredinu u eri velike ekspanzije novih tehnoloških procesa i kako smanjiti njihov negativni uticaj na prirodno okruženje. Imajući u vidu ograničene rezerve prirodnih resursa i negativni uticaj na životnu sredinu prilikom njihove potrošnje, bilo je neophodno uvesti nove pristupe i modele za njihovo održivo korišćenje. Principi održivog razvoja imaju za cilj usaglašavanje politike i strategije nacionalnog i socijalnog razvoja na takav način da se eliminišu svi negativni uticaji na prirodu i prirodne izvore koji su važni za sve vidove ljudskih aktivnosti u budućnosti. Zaštita životne sredine je izuzetno važana u svim zemljama i u direktnoj je vezi sa stepenom ekonomskog razvoja i nivoa edukacije stanovništa o značaju zdrave životne sredine I načinu njenog očuvanja. Ubrzani tehnološki razvoj dovodi do poboljšanja kvaliteta života u svim sferama ljudske aktivnosti, ali paralelno sa tim stvara se mogućnost veće degradacije životne sredine
Differences in coating mechanism of structurally different aluminosilicates observed through the thermal analysis
No full textSystematic modification of three structurally different minerals (zeolite, mica, and vermiculite) was carried out with the aim of determining the modification mechanism and exposing the hydrophobic surface that can be used as a sorbent for many organic compounds. Mechanism of modification with cationic surfactant depends strongly on the mineral type. In order to identify the influence of aluminosilicates structural differences on the modification process, adsorption experiments with organic matter and water vapor, supplemented with the DTA/TG analysis, were performed. The cation exchange capacity (CEC) value was 1454>560>28meqkg(-1) for zeolite (clinoptilolite), vermiculite, and mica (muscovite), respectively. Despite its CEC value, vermiculite adsorbed three times the amount of organic matter than did clinoptilolite due to the porous structure of zeolite, which acted to limit the adsorption only on the external exchangeable cations. If the loading amount is equal to the CEC or the external cation exchange capacity for clinoptilolite (ECEC approximate to 10% CEC), the monolayer will form while mineral surface will have hydrophobic character. Only one active center exists at the surface of the clinoptilolite that was identified by DTA curves with a sharp and defined peak around 300 degrees C and by the mass loss at the TG diagrams. Two significant and equal active centers were observed in vermiculite, one for the exchange of the surface cations and the other for the interlayer cations and H2O molecules. Muscovite CEC is negligible, and due to the absence of any other functional groups, the modification of this mineral was impossible
Determination of the phenolic profile of peach (Prunus persica L.) kernels using UHPLC-LTQ OrbiTrap MS/MS technique
No full textRecently, search for new natural sources of compounds with health-enhancing properties prompted interest in fruit kernels. This paper aims to assess peach kernels as a source of nutritionally important compounds, such as phenolic compounds. A total of 25 kernels from various peach germplasm differing in origin and ripening time were characterized by their phenolic profiles. Ultra-high-Performance Liquid Chromatography coupled with Linear Trap Quadrupole and OrbiTrap MS/MS hybrid mass spectrometry was used for determination of 76 different organic compounds. The content of identified phenolic compounds indicated peach kernel as reliable source of bioactive substances with prevalent concentrations of catechin and several phenolic acids. Statistical procedures confirm that phenolic compounds could be used as phytochemical biomarkers to differentiate peach kernel samples belonging to different cultivars/genotypes according to their origin and ripening time. The CATPCA confirmed the possibility of application of chemical profiles presented only as categorical variables for classification
Potentiation of the ibuprofen antihyperalgesic effect using inorganically functionalized diatomite
No full textRefined diatomite from the Kolubara coal basin (Serbia) was inorganically functionalized through a simple, one-pot, non-time-consuming procedure. Model drug ibuprofen was adsorbed on the functionalized diatomite under optimized conditions providing high drug Loading (similar to 201 mg g(-1)). Physicochemical characterization was performed on the starting and modified diatomite before and after ibuprofen adsorption. Dissolution testing was conducted on comprimates containing the drug adsorbed on the modified diatomite (composite) and those containing a physical mixture of the drug with the modified diatomite. The antihyperalgesic and the antiedematous activity of ibuprofen from both composites and physical mixtures were evaluated in vivo employing an inflammatory pain model in rats. Functionalization and subsequent drug adsorption had no significant effect on the diatomite ordered porous structure. Two forms of ibuprofen most likely coexisted in the adsorbed state - the acidic form and a salt/complex with aluminium. Both comprimate types showed extended ibuprofen release in vitro, but no significant influence on the duration of the ibuprofen effect was observed upon in vivo application of the composite or physical mixture. However, both the composite and the physical mixture were more effective than equivalent doses of ibuprofen in pain suppression in rats. This potentiation of the ibuprofen antihyperalgesic effect may result from the formation of the drug complex with the carrier and can be of clinical relevance
Sintering, crystallization and foaming of La2O3 center dot SrO center dot 5B(2)O(3) glass powders - effect of the holding temperature and the heating rate
No full textThe peculiarities of sinter-crystallization of La2O3 center dot SrO center dot 5B(2)O(3) fine glass powder (below 1 mu m) are investigated and discussed. The sintering was studied by contactless optical dilatometry and porosity measurements. The crystallization process was evaluated by differential scanning calorimetry (DSC) and the crystalline phase formation was analyzed by X-ray diffraction (XRD). Finally the microstructures of the samples sintered at different temperatures were observed by field emission scanning electron microscope (FESEM). The specific aim of this study was to highlight the influence of sintering temperature and heating rate on the densification process and the final structure of glass-ceramic samples. It was shown that zero water adsorption and minimum closed porosity of similar to 3% were obtained at heating rate of 2 degrees C/min and at about 1 h holding at 690 degrees C. The temperature increase accelerated intense foaming process that resulted in formation of total porosity of 35-45%. It was also demonstrated that the foaming depended on the heating rate: the higher the heating rate - the more intensive was the bloating. The observed foaming process was related to intensive crystallization and re-crystallization of La2O3 center dot SrO center dot 5B(2)O(3) crystal phase. The phase formation processes entirely completed after 30-60 min at 730-740 degrees C with the formation of intriguing and unusual crystal structures
Molybdenum recovery as alloying agent from waste molybdenum solution
No full textU istraživačkom radu opisan je komercializovan reciklažni proces prerade otpadnog rastvora iz postrojenja za proizvodnju sijaličnih vlakana od volframa radi izdvajanja molibden (VI)-oksida i njegovom daljem iskorišćavanju kao legirajućeg agensa sivog liva. U prvom delu izvršena je neutralizacija utrošene kiseline, koja u sebi sadrži izvesne količine molibdena, uz pomoć rastvora amonijaka, a potom kristalizacija i filtracija amonijum-molibdata, njegovo sušenje i prženje u cilju dobijanja praha molibdentrioksida tehničke čistoće (maseni udeo molibdena 59,2 mas%). U drugom delu izvršeno je legiranje sivog liva uz pomoć MoO3 u indukcionoj peći. Finalni proizvod je legura železa sa povećanom tvrdoćom uz postignut visok stepen usvajanja molibdena u leguri (čak do 86%).The present work reports the commercialization of a recycling process of spent acid from filament tungsten wire plant to recover molybdenum (VI)-oxide and further utilizing this product for alloying cast iron. First part of the process consists of ammonia gas neutralization of spent acid containing molybdenum, crystallization and filtration of ammonium molybdate, drying and roasting to produce a commercial grade molybdic-trioxide powder (molybdenum mass fraction 59.2 mas%). Second part of the process consists of grey cast alloying with MoO3 in inducing furnace. Final product was hardened iron alloy with high yield of molybdenum recovery (up to 86 %)