Dubina difuzije organskih molekula u gleđnom tkivu kod pasa

The objective of this study was to evaluate the extent of diffusion of organic molecules in the enamel tissue, of permanent teeth. The experimental study was performed in vivo on dogs. To the experimental dogs the molars on the right side of the lower jaw underwent enamel tissue reduction without additionally placing any tooth protection. Teeth on the left side of the lower jaw were left intact thus representing the control. After 12 months animals were sacrificed, experimental and control teeth extracted and the study of diffusion in vitro carried on. For that purpose an organic spin marker 4-amino - 2,2,6,6,-tetramethyl-piperdinyl 1-oxi (4-Amino-Tempo) was selected. The property of this marker is that it contains a nitroxide radical which is stable in a neutral and base environment, and due to the unbound spin of the free radical it is highly suitable for the electronic paramagnetic resonance method (EPR). Studies on the diffusion of organic spin markers in the enamel tissue are performed by submerging the prepared tooth in a water solution containing the marker substance. From the intensity of the EPR spectrum filmed after tooth withdrawal from the water solution, distribution diffusion time and penetration depth of marker molecules were established. Coefficients of organic spin marker diffusion and saturation concentrations of marker molecules in the enamel were determined. The observed variations in the area! and time for distribution of diffused molecules were explained by the binding possibility of the NO-radical from the marker molecule to the enamel tissue. The results of the experiment contained in this work contribute to a better understanding of the spin marker organic molecule movement through the enamel tissue which is controlled by the mechanism of diffusion and chemical bonding of the marker molecule to the enamel structure. The results of the experimental research also indicate the harmful effects of leaving the enamel tissue without protection.U ovom radu prikazani su rezultati dubine difuzije organskih molekula u gleđnom tkivu stalnih zuba. Eksperimentalna istraživanja in vivo vršena su na psima. Na molarima desne strane donje vilice, kod svih životinja eksperimentalno je izvršena redukcija gleđnog tkiva, bez postavljanja zaštite, dok su zubi leve strane mandibule ostali intaktni i predstavljali su kontrolnu grupu. Period in vivo je trajao 12 meseci, posle čega su životinje žrtvovane, eksperimentalni I kontrolni zubi izolovani I nastavljeno ispitivanje procesa difuzije in vitro. U te svrhe izabran je organski spinski marker 4-amino-2,2,6,6-teramentil-piperidinil-1-oksi (4-Amino Tempo). Osobina ovog markera je da ima u svom sastavu nitroksidni radikal koji je stabilan u neutralnoj i baznoj sredini, a zbog nesparenog spina slobodnog radikala veoma je pogodan za istraživanja metodom elektronske paramagnetne resonance

Ispitivanje mogućnosti vezivanja organskih molekula u strukturi kristala gleđnog tkiva psa

The main objective of this paper is to determine the possibilities of binding organic molecules to the enamel crystal structure. The experimental study in vivo was performed on maxillar molars in dogs. Time in vivo was 12 months after which animals were executed. All intact teeth were extracted and the study of the enamel crystal structure was continued in vitro. After treating the enamel tissue with the solution of organic spin marker 4-Amino-Tempo, the follow-up of the changes of values of the apatite crystal unit cell parameters was done by X-ray diffraction. The following conclusions may be reached after evaluation of the obtained results: in addition to the process of diffusion through the interprysmatic space of the enamel tissue, the organic molecules also play a crucial role in the changes of the crystal grid size, due to binding of organic parts of molecules in the enamel crystal structure. Permanent oscillations of the existing oxygen bonds in the enamel crystal structure have been determined every few weeks and depend on the process of substitution and resubstitution of OH ions by ions from organic and inorganic molecules and various dental materials. The local application of the fluorine based preparations on permanent teeth must be repeated every two months due to breakedown of oxygen bond and resubstitution.Osnovni cilj ovog rada je bio ispitivanje mogućnosti vezivanja organskih molekula u strukturi kristala gleđnog tkiva. Eksperimentalna istraživanja in vivo vršena su na maksilarnim molarima pasa. Nakon isteka perioda od 12 meseci životinje su žrtvovane, svi zdravi molari izvađeni i nastavljeno je ispitivanje kristalne strukture gleđnog tkiva in vitro. Korišćena je metoda difrakcije X zrakova koja u okviru kristalografskih analiza jedino ima toliku osetljivost da se mogu uočiti i najmanje promene u dimenziji kristalne rešetke gleđnog tkiva tretiranog vodenim rastvorom organskog spinskog markera 4-Amono - Tempo. Na osnovu rezultata obavljenih istraživanja zaključeno je da organski molekuli, pored procesa difuzije kroz interprizmatične prostore gleđnog tkiva, igraju presudnu ulogu i u promenama dimenzija kristalne rešetke zbog vezivanja organskih delova molekula u strukturi kristala gleđi. Permanentne oscilacije broja difundovanih molekula markera u gleđi, ukazuju na proces njihovog vezivanja za strukturu gleđi koja na svakih nekoliko nedelja predstavlja supstituciju i resupstituciju OH jona iz kristalne rešetke gleđi sa organskim, neorganskim ili česticama iz nekih lokalno aplikovanih dentalnih materijala. Lokalno aplikovani preparati na bazi fluora moraju se svaka 2 meseca ponovo postavljati na gleđno tkivo stalnih zuba zbog resupstitucije i izlaska jona fluora iz kristalne rešetke apatita

Mesiodens and paramolar in the medieval age skeletal remains

Evolution as in all segments of human behavior and existence has left traces on human teeth. The aim of this study was to determine the frequency of the supernumerary teeth in skeletal remains found at the archeological site Stara Torina and SEM evaluation of the changes on the supernumerary teeth. The study included 90 skulls and 81 jaws of both sexes with average age 20-60 years. Supernumerary teeth were prepared for SEM for analyzing dental tissues. Six supernumerary teeth were found, among them five mesiodensand one paramolar. The frequency of hyperdontia in these skeletal remains is 2,1%. Mesiodens is different morphologically from the incisor it replaced and took part in occlusal contacts during mastication. Paramolar is different morphologically from molar teeth and it did not take part in occlusal contacts during mastication because of its low adherence for bone tissues and small dimensions

Određivanje boje zuba kod pasa

Tooth color depends on hard tooth tissue structures, above all dentine, and is genetically determinated. Nutritive habits and nutrition patterns during the lifetime can influence the change of crystal structure of enamel and dentine and consequently tooth color. The purpose of this research is to determine the color of dog teeth and to compare it to human tooth color. Standardized color key was used, thus overcoming all three color parameters: main color - hue, satiate - chroma and brightness - value. The obtained results show that both colors of dog and human teeth belong to the same spectrum. Dog teeth more frequently have a darker color which can be connected to the fact that their teeth are more worn and consequently a more intensive diffusion process is undergoing due to the changes in crystal structure because of the newly formed bondings of organic molecules into the crystal structure of the enamel.Boja zuba zavisi od sastava tvrdih zubnih tkiva, pre svega dentina i genetski je određena. Obrazac ishrane i nutritivne navike mogu u toku života putem difuzije uticati na promenu kristalne strukture gleđi i dentina a posledično i na boju zuba. Cilj rada je utvrditi boju zuba pasa i uporediti je sa bojom zuba ljudi. Korišćen je standardizovan ključ za boje kojim je moguće obuhvatiti određivanje sva tri parametra boje: osnovnu boju - hue, zasićenost - chroma i svetlinu - value. Dobijeni rezultati pokazuju da boja zuba i pasa i ljudi u najvećem broju slučajeva pripada istom spektru. Kod pasa su zastupljenije tamnije nijanse, što se dovodi u vezu sa većom abradiranošću površina njihovih zuba i intenzivnijom difuzijom i promenama dimenzija kristalne rešetke zbog vezivanja organskih delova molekula u strukturi kristala gleđi

Photocatalytic activity of doped titanium(IV)-oxide in degradation processes of some pesticides

Kao što je poznato, RS-2-(4-hlor-o-toliloksi)propionska kiselina (MCPP), (4-hlor-2-metilfenoksi)sirćetna kiselina (MCPA) i 3,6-dihlorpiridin-2-karboksilna kiselina  (klopiralid) su herbicidi sa veoma širokim spektrom dejstva, a pored toga su rastvorljivi u vodi, teško biorazgradljivi i prema literaturnim podacima su, nažalost, veoma često prisutni herbicidi u pijaćoj vodi. Proces heterogene fotokatalize uz primenu TiO2i UV zračenja se pokazao kao veoma pogodan način za njihovo uklanjanje iz vode. Međutim, zbog velikog energetskog procepa od 3,2 eV (anataze-oblik), odnosno, 3,0 eV (rutil-oblik), veoma mali udeo bliskih UV zraka iz sunčeve svetlosti (oko 3−4%) biva iskorišćen u toku fotokatalitičkog procesa, što ukazuje na to da je TiO2 praktično neaktivan u prisustvu sunčeve svetlosti. Na osnovu literaturnih podataka je zapaženo da postoji mogućnost fotorazgradnje pojedinih supstrata u prisustvu TiO2 primenom vidljive svetlosti. Na primeru MCPP je ispitana aktivnost TiO2 Degussa P25 kao fotokatalizatora u prisustvu vidljive svetlosti. Na osnovu refleksionih spektara je utvrđeno da MCPP adsorbovan na TiO2 Degussa P25 apsorbuje vidljivi deo spektra (λ ≥400 nm). Nastali prelazni kompleks je potvrđen FTIR merenjima. Efikasnost TiO2Degussa P25 primenom vidljive svetlosti je upoređena sa sunčevim i UV zračenjem, kao i direktnom fotolizom u prisustvu pomenutih izvora zračenja. Brzina fotokatalitičke razgradnje MCPP primenom vidljive svetlosti iznosi 0,86 μmol dm−3min−1, što je oko 4 puta brže u poređenju sa direktnom fotolizom. Nadalje je ustanovljena optimalna masena koncentracija katalizatora od oko 8 mg cm−3, koja je znatno viša u poređenju sa primenom UV zračenja. Razlog je najverovatnije različit mehanizam fotorazgradnje koji se odvija primenom vidljivog i UV zračenja. Naime, prisustvo 2-metil-2-propanola (poznatog hvatača •OH-radikala) praktično ne utiče na brzinu fotokatalitičke razgradnje MCPP p rimenom vidljive svetlosti, što ukazuje da se mehanizam razgradnje MCPP primenom  vidljive svetlosti ne odvija posredstvom •OH-radikala, za razliku od onog uz primenu UV zračenja. S obzirom da se katalizator TiO2 Degussa P25 uz primenu vidljive svetlosti nije  pokazao kao naročito efikasan kada je u pitanju razgradnja sva tri herbicida i imajući u vidu da se u poslednje vreme iz razloga praktične primene sve više pribegava procesu dopovanja TiO2 različitim tipovima metala (alkalnih, zemnoalkalnih, prelaznih i dr.) i nemetala (halogenida, halkogenida i dr.), u okviru ove doktorske disertacije je ispitana aktivnost N-TiO2 (sintetisanih mokrim i suvim putem) i TiO2 (rutil) dopovanog sa različitim količinama Fe3+-jona (0,13−1,48 at.%) pri razgradnji herbicida MCPP i MCPA primenom vidljive svetlosti. Pored toga je ispitana efikasnost TiO2 (anataze) takođe dopovanog sa različitim količinama Fe3+-jona (0,71−1,80 at.%) na primeru MCPP.  Poredeći N-TiO2 (sintetisan mokrim putem) i N-TiO2 (sintetisani suvim putem), primećeno je da je u drugom slučaju efikasnost katalizatora veća oko 2 puta. Isto tako je zapažena u slučaju MCPP nešto veća fotokatalitička aktivnost N-TiO2 (sintetisani suvim putem) u poređenju sa TiO2 (anataze). Kada je u pitanju MCPA aktivnost sva tri katalizatora je veoma slična. Pored toga je zapažena veća efikasnost N-TiO2 (sintetisan mokrim putem) u poređenju sa TiO2 Degussa P25 (oko 1,5 puta) i oko 5 puta u odnosu na direktnu fotolizu, dok su N-TiO2 (sintetisani suvim putem) oko 3 puta efikasniji u poređenju sa TiO2 Degussa P25 i oko 10 puta u  poređenju sa direktnom fotolizom. Brzina solarne razgradnje je preko 100 puta manja nego primenom vidljivog i UV zračenja, što je posledica različitih intenziteta pomenutih izvora ozračivanja i različitih uslova pri kojima je vršena razgradnja.  Ustanovljena je optimalna masena koncentracija N-TiO2 (sintetisan mokrim putem) od 4 mg cm−3. Prilikom razgradnje MCPP i MCPA je nađeno da je brzina veća kada se kao katalizator  koristi TiO2 (rutil) u poređenju sa Fe-TiO2 i da sa povećanjem količine Fe3+-jona fotokatalitička aktivnost uglavnom opada. Kada je kao fotokatalizator korišćen TiO2   (anataze) dopovan različitim količinama Fe3+-jona (od 0,71 do 1,80 at.%), razgradnja  MCPP je u svim slučajevima znatno sporija u odnosu na TiO2 (anataze). S obzirom da su prema literaturnim podacima kinetika i mehanizam fotokatalitičke  razgradnje klopiralida nepoznati, ispitana je njegova stabilnost pri različitim eksperimentalnim uslovima. Tokom ispitivanja uticaja pH kako u prisustvu, tako i u odsustvu dnevne svetlosti u intervalu pH od 1,0−9,0, nađeno je da ni u jednom slučaju ne dolazi do razgradnje supstrata u periodu od sedam meseci koliko je proces praćen. Takođe je ispitana kinetika fotokatalitičke razgradnje klopiralida primenom UV i vidljivog zračenja u prisustvu TiO2 Degussa P25, kao i direktna fotoliza primenom oba izvora zračenja. Nađeno je da je brzina fotokatalitičke razgradnje primenom UV zračenja veća oko 5 puta u odnosu na direktnu fotolizu. Za praćenje toka fotokatalitičke razgradnje klopiralida je izabrana pH-vrednost od 3,2. Nadalje je zapaženo da se u ispitivanom opsegu početnih koncentracija supstrata (0,5–3,0 mmol dm−3) kinetika fotokatalitičke razgradnje klopiralida može opisati pseudo-prvim redom. Pri ispitivanju uticaja masene koncentracije katalizatora (0,5–8 mg cm−3) na brzinu razgradnje klopiralida, ustanovljena je optimalna masena koncentracija primenjenog fotokatalizatora od oko 4 mg cm−3. Izračunata ukupna  prividna energija aktivacije iznosi 7,74 kJ mol−1. Pored toga, prisustvo kiseonika ubrzava reakciju 2 puta, dok dodatak elektron-akceptora kao što su (NH4)2S2O8, H2O2 i KBrO3 pokazuje značajan i različit efekat na kinetiku fotokatalitičke razgradnje klopiralida. Pri ispitivanju uticaja etanola, kao hvatača slobodnih radikala, nađeno je da se heterogena fotokataliza odvija uglavnom preko •OH-radikala. Na osnovu LC–MS/MS (ESI+) merenja ustanovljeno je prisustvo nekoliko intermedijera: 3,6-dihlor-piridin-2-ol, 3,6-dihlor hidroksipiridin-2-karboksilna kiselina i 3,3',6,6'-tetrahlor-2,4'-bipiridin-2'-karboksilna kiselina. Na osnovu identifikovanih intermedijera, kao i kinetičkih rezultata, predložen je mogućput mehanizma fotokatalitičke razgradnje klopiralida. Prilikom ispitivanja uticaja strukture molekula na brzinu razgradnje, konstatovano  je da u slučaju klopiralida praktično ne dolazi do fotokatalitičke razgradnje u prisustvu TiO2 (anataze) i N-TiO2 (sintetisani suvim putem) uz primenu vidljive svetlosti, kao i u slučaju TiO2 Degussa P25. Pored toga, primenom TiO2 (rutil) i Fe-TiO2 kao fotokatalizatora, sa povećanjem količine Fe3+-jona od 0,13 do 1,27 at.% raste brzina razgradnje klopiralida, ukazujući da strukturne osobine supstrata utiču na brzinu njihove razgradnje.It is well known that RS-2-(4-chloro-o-tolyloxy)propionic acid (MCPP), (4-chloro-2- methyl-phenoxy)acetic acid (MCPA) and 3,6-dichloropyridine-2-carboxylic  acid (clopyralid) are herbicides of wide activity spectrum. They are soluble in water, hardly biodegradable and, unfortunately, often present in drinking water. Heterogeneous photocatalysis by application of TiO2 and UV radiation proved to be very suitable for their removal from water. However, due toits large energy gap, i.e. 3.2  eV (anatase-form) and 3.0 eV (rutile-form), a very small fraction of sunlight in the near UV range (about 3–4%) is used during photocatalytic process, which is an indication of TiO2 inactivity in the presence of this light source. Some literature data report on the possibility of photodegradation of certain substrates by visible light in the presence of TiO2. MCPP served as substrate for testing TiO2 Degussa P25  photocatalytic activity in the presence of visible light. On the basis of reflection spectra it was established that MCPP adsorbed on TiO2 Degussa P25 was absorbing visible spectrum radiation (λ ≥400 nm). The existence of thus formed  charge-transfer complex was confirmed with FTIR analysis. The efficiency of  TiO2 Degussa P25 with application of visible light was compared to sunlight and UV radiation, as well to directphotolysis in the presence of these light sources. The rate of MCPP photocatalytic degradation by means of visible light is 0.86 μmol dm−3 min−1, which is about 4 times faster than direct photolysis. In addition, the optimal  catalyst concentration of about 8 mg cm−3, much higher than using UV radiation,  was established. The reason is, probably, a different mechanism of  hotodegradation  in the presence of visible and UV irradiation. Namely, the presence of 2-methyl-2-propanol (well-known •OH radical scavenger) has practicallyno effect on the rate of  MCPP photocatalytic degradation using visible light, which points that this degradation mechanism does not involve •OH radicals, in contrast to that established  for UV radiation. Since the catalyst TiO2 Degussa P25 with application of visible light was not very  efficient in degradation of all three herbicidesand in view that nowadays is very  popular doping process of TiO2 with different types of metals (alkali, alkaline-earth, transition, etc.) and non-metals (halogen, chalcogen, etc.), in the scope of this Ph.D.  thesis activities of N-TiO2 (synthesized by wet and dry procedure) and TiO2 (rutile) doped with various amounts of Fe3+ (0.13–1.48 at.%) in degradation processes of  herbicides MCPP and MCPA using visible light were studied. In addition, the efficiency of TiO2 (anatase) doped with various amounts of Fe3+ (0.71–1.80 at.%) was also tested for MCPP degradation. When comparing N-TiO2 (synthesized by wet procedure) and N-TiO2 (dry procedure), it was observed that in the latter case the catalyst efficiency was about two times higher. In this case for MCPP was also observed somewhat higher photocatalytic activity of N-TiO2 (synthesized by dry procedure) in comparison with TiO2. When activities of all three catalysts towards MCPA are compared, the results are very alike. In addition, higher efficiency of N-TiO2  (wet procedure) comparing to TiO2 Degussa P25 (about 1.5 times) and about 5 times in comparison to direct photolysis were recorded, while N-TiO2 (dry procedure) was about 3 times more efficient than TiO2 Degussa P25 and about 10 times in comparison with direct photolysis. The rate of solar degradation is about 100 times lower than by application of UV and visible radiation, as a consequence of various intensities of the mentioned light sources and different conditions of photodegradation. An optimal concentration of N-TiO2 (wet procedure) of 4 mg cm−3  was established. During degradation of MCPP and MCPA it was observed that the rate is higher if TiO2 (rutile) was applied comparing to Fe-TiO2 and with increasing amount of Fe3+ photocatalytic activity mostly decreases. When TiO2 (anatase) doped with various amounts of Fe3+ (0.71 to 1.80 at.%) was applied for MCPP degradation, the process was much slower than with undoped catalyst. Since we have not found relevant literature data on kinetics and mechanism of photocatalytic degradation of clopyralid, its stability in different experimental conditions was tested. In investigating of influences of pH (1.0–9.0) both in presence and in absence of daylight, in no cases decomposition was observed during seven months experiments. Also, the kinetics of photocatalytic degradation of clopyralid using UV and visible irradiation in the presence of TiO2 Degussa P25 and in direct photolysis by application of both irradiation sources was studied. It was found that the  rate of photocatalytic decomposition using UV radiation was 5 times higher comparing to direct photolysis. For clopyralid photocatalytic monitoring a pH value of  3.2 was chosen. In addition, in the investigated concentration range (0.5–3.0 mmol  dm−3) the photocatalytic degradation kinetics of clopyralid in the first stage of the reaction follows approximately a pseudo-first kinetic order. In investigation of influence of catalyst concentration (0.5–8 mg cm−3) on the rate of clopyralid degradation the highest reaction rate was observed at 4 mg cm−3 of catalyst concentration The apparent activation energy of the reaction being 7.74 kJ mol−1. The absence of molecular oxygen resulted in a significant decrease (about 2 times) in the rate of clopyralid photodegradation. The effect of the presence of (NH4)2S2O8, H2O2 and KBrO3, acting as electron acceptors along with molecular oxygen affects clopyralid photocatalytic degradation considerably and indifferent ways. By studying the effect of ethanol as a hydroxyl radical scavenger it was shown that the heterogeneous catalysis takes place mainly via •OH radicals. LC−MS/MS (ESI+) monitoring of the process showed that several pyridine-containing intermediates are formed: 3,6-dichloropyridin-2-ol, 3,6-dichloro hydroxypyridine-2-carboxylic acid and 3,3',6,6'-tetrachloro-2,4'-bipyridine-2-carboxylic acid. Based on the identified intermediates and overall kinetic results, a probable photocatalytic degradation mechanism was proposed.  Finally, in the case of clopyralid it was established that practically no degradation  occurs in the presence of TiO2 (anatase) and N-TiO2 (dry procedure) with visible light  and also with TiO2 Degussa P25. Besides of that, by using TiO2 (rutile) and Fe-TiO2 as photocatalysts it was noted that increasing the concentration of Fe3+ from 0.13 to 1.27 at.% comes to increasing photodegradation rate of clopyralid. Results indicate that differences in molecular structure of chosen compound, influence obtained photocatalytic activity to a great extent

Analiza deformacija donje vilice optičkom metrologijom

Background/Aim. New optical stereometric methods based on both contact and noncontact mechanisms for displacement measurement have become common methods in biomechanical behavior research of biomaterials, bone and soft tissue. The aim of this study was to register and measure possible deformations of the lower jaw (mandible) with the intact dental arch using optical metrology method. Methods. The system for full field measurement of deformations (strains) comprised of two digital cameras for a synchronized stereoview of the specimen, and the Aramis software. Results. The maximum mandibular bone strains were measured in the regions of the lower first premolar and the lower second molar. In the action force of 500 N simulated in the region of the first lower premolar the intensity of deformation was 86 μm. The value of maximum strain in the bone around the molars was 24 μm for the force of 500 N acting on the second lower molar. When it comes to premolars, 3-5 times stronger deformation was observed in the region of the first lower premolar, compared to the deformation values of the second lower premolar area. Conclusion. Under loading of the applied forces the measured strains were in the elastic deformation area, meanning that the dependence of force and deformity is linear. The highest values of strain measurements obtained by the optical method were found in the jaw bone tissue around the loading teeth, and the bony regions of the triangle and mental region. According to the obtained results from the Aramis processing software it can be concluded that this method is applicable in a variety of biomedical research.Uvod/Cilj. Nove optičke stereometrijske metode koje se zasnivaju na kontaktnim i nekontaktnim mehanizmima za merenje zapremine postaju uobičajene metode u istraživanju biomehaničkog ponašanja biomaterijala, koštanog i mekog tkiva. Cilj ove studije bio je da se optičkom metodom merenja registruju i izmere eventualne deformacije koštanog fundamenta donje vilice sa intaktnim zubnim nizom i da se, ujedno, prikažu mogućnosti primene optičke metrologije u istraživanjima u stomatologiji. Metode. Sistem za merenje deformacija ispitivane donje vilice sa intaktnim zubnim lukom obuhvatio je dve digitalne kamere koje obezbeđuju stereosinhronizovani prikaz primerka, i softver Aramis. Rezultati. Najveće deformacije koštanog tkiva donje vilice izmerene su u regionu donjeg prvog premolara i donjeg drugog molara. Pri delovanju sila od 500 N za region prvog donjeg premolara veličina deformacije bila je 86 μm. Vrednost maksimalne srednje deformacije u koštanom sistemu oko molara iznosila je 24 μm pri delovanju sile od 500 N na drugi donji molar. Kada su u pitanju premolari, 3-5 puta jače deformacije uočene su u regionu prvog donjeg premolara, nego u predelu drugog donjeg premolara. Zaključak. Prilikom delovanja primenjenih sila deformacije se nalaze u elastičnom deformacionom polju, a međusobna zavisnost sile i deformacije ima linearan karakter. Najveće vrednosti deformacija dobijene optičkom metodom merenja registruju se u koštanom tkivu donje vilice koja je u neposrednom kontaktu sa zubima koji se opterećuju, kao i u koštanim regionima zakutnjačkog trougla i bradnog (mentalnog) otvora. Na osnovu analize rezultata dobijenih primenom softvera Aramis može se reći da postoje mogućnosti primene ove metode u različitim biomedicinskim istraživanjima

Biomechanical interactions between bone and metal-ceramic bridges composed of different types of non-noble alloys under vertical loading conditions

The purpose of this study was to compare the mechanical properties of three metal-ceramic bridges of different types of dental alloys and to present and evaluate the possible biomechanical interactions between a marginal bone and metal-ceramic bridges during vertical loading. The research was done as an experimental study. A mandible with an intact anterior region was used. The preparation of the remaining teeth for receiving three types of porcelain-fused-to-metal (PFM) restorations was performed. Vita VMK 95 was used for all three metal-ceramic restorations. These three metal-ceramic bridges composed of different alloys, nickel and non-nickel, served as different models: the Niadur-nickelferous model, the Wiron 99-nickel model and the Wirobond C-cobalt-chrome model. The maximum compressive strain of 5% for all three virtual models is observed in the region of central incisors. The Niadur model has the lowest mean strain (2.62%) in comparison with the other two models. The mean strain of Wiron 99 is lower, by 0.10%, than the mean strain of the Wirobond model. Biomechanical behavior of the presented models caused by the vertical-loading conditions is explained as an interaction between the marginal bone and the metal-ceramic bridges. All of them, nickel and non-nickel models, indicate a similar strain (deformation) distribution; however, from the biomechanical perspective, Niadur is more favorable than the other two materials

Analysis of Alternative Fuel Usage in Air Transport

U zračnom se prometu danas velikom većinom koriste fosilna goriva za pokretanje zrakoplova kao što je na primjer kerozin. Korištenje fosilnog goriva rezultira u golemim emisijama stakleničkih i otrovnih plinova u atmosferu za vrijeme leta zrakoplova. To posebice utječe na povećanje Zemljine temperature koje prouzrokuje globalno zatopljenje. Zbog tog problema počinju se detaljno proučavati različiti alternativni izvori energije u zračnom prometu koji bi ispušne plinove sveli na minimum. To uključuje različite mješavine biogoriva s kerozinom, ali i nove, inovativne tehnologije kao što su tekući dušik, električna, solarna i nuklearna energija. Implementacija biogoriva je već započela kod nekih zrakoplovnih prijevoznika tako da je njena budućnost svijetla. Također se provode brojna istraživanja vezana za električni pogon zrakoplova koji bi mogao svesti emisije plinova na nulu.In air traffic today, fossil fuels are mostly used to fly planes, for example kerosene. The use of fossil fuels results in enormous emissions of greenhouse and toxic gases into the atmosphere during flight. This affects the increase in Earth's temperature, which causes global warming. Due to this problem, various alternative sources of energy in air traffic are being detailly researched, which would minimize the emissions of gases. These include various blends of kerosene biofuels, but also new and innovative technologies such as liquid nitrogen, electric, solar and nuclear energy. The implementation of biofuels was already made by some airlines, so the future is bright. Numerous studies have also been carried out regarding the electric propulsion of aircraft that could result in zero emissions

Analysis of Alternative Fuel Usage in Air Transport

U zračnom se prometu danas velikom većinom koriste fosilna goriva za pokretanje zrakoplova kao što je na primjer kerozin. Korištenje fosilnog goriva rezultira u golemim emisijama stakleničkih i otrovnih plinova u atmosferu za vrijeme leta zrakoplova. To posebice utječe na povećanje Zemljine temperature koje prouzrokuje globalno zatopljenje. Zbog tog problema počinju se detaljno proučavati različiti alternativni izvori energije u zračnom prometu koji bi ispušne plinove sveli na minimum. To uključuje različite mješavine biogoriva s kerozinom, ali i nove, inovativne tehnologije kao što su tekući dušik, električna, solarna i nuklearna energija. Implementacija biogoriva je već započela kod nekih zrakoplovnih prijevoznika tako da je njena budućnost svijetla. Također se provode brojna istraživanja vezana za električni pogon zrakoplova koji bi mogao svesti emisije plinova na nulu.In air traffic today, fossil fuels are mostly used to fly planes, for example kerosene. The use of fossil fuels results in enormous emissions of greenhouse and toxic gases into the atmosphere during flight. This affects the increase in Earth's temperature, which causes global warming. Due to this problem, various alternative sources of energy in air traffic are being detailly researched, which would minimize the emissions of gases. These include various blends of kerosene biofuels, but also new and innovative technologies such as liquid nitrogen, electric, solar and nuclear energy. The implementation of biofuels was already made by some airlines, so the future is bright. Numerous studies have also been carried out regarding the electric propulsion of aircraft that could result in zero emissions

Photocatalytic activity of doped titanium(IV)-oxide in degradation processes of some pesticides

Kao što je poznato, RS-2-(4-hlor-o-toliloksi)propionska kiselina (MCPP), (4-hlor-2-metilfenoksi)sirćetna kiselina (MCPA) i 3,6-dihlorpiridin-2-karboksilna kiselina  (klopiralid) su herbicidi sa veoma širokim spektrom dejstva, a pored toga su rastvorljivi u vodi, teško biorazgradljivi i prema literaturnim podacima su, nažalost, veoma često prisutni herbicidi u pijaćoj vodi. Proces heterogene fotokatalize uz primenu TiO2i UV zračenja se pokazao kao veoma pogodan način za njihovo uklanjanje iz vode. Međutim, zbog velikog energetskog procepa od 3,2 eV (anataze-oblik), odnosno, 3,0 eV (rutil-oblik), veoma mali udeo bliskih UV zraka iz sunčeve svetlosti (oko 3−4%) biva iskorišćen u toku fotokatalitičkog procesa, što ukazuje na to da je TiO2 praktično neaktivan u prisustvu sunčeve svetlosti. Na osnovu literaturnih podataka je zapaženo da postoji mogućnost fotorazgradnje pojedinih supstrata u prisustvu TiO2 primenom vidljive svetlosti. Na primeru MCPP je ispitana aktivnost TiO2 Degussa P25 kao fotokatalizatora u prisustvu vidljive svetlosti. Na osnovu refleksionih spektara je utvrđeno da MCPP adsorbovan na TiO2 Degussa P25 apsorbuje vidljivi deo spektra (λ ≥400 nm). Nastali prelazni kompleks je potvrđen FTIR merenjima. Efikasnost TiO2Degussa P25 primenom vidljive svetlosti je upoređena sa sunčevim i UV zračenjem, kao i direktnom fotolizom u prisustvu pomenutih izvora zračenja. Brzina fotokatalitičke razgradnje MCPP primenom vidljive svetlosti iznosi 0,86 μmol dm−3min−1, što je oko 4 puta brže u poređenju sa direktnom fotolizom. Nadalje je ustanovljena optimalna masena koncentracija katalizatora od oko 8 mg cm−3, koja je znatno viša u poređenju sa primenom UV zračenja. Razlog je najverovatnije različit mehanizam fotorazgradnje koji se odvija primenom vidljivog i UV zračenja. Naime, prisustvo 2-metil-2-propanola (poznatog hvatača •OH-radikala) praktično ne utiče na brzinu fotokatalitičke razgradnje MCPP p rimenom vidljive svetlosti, što ukazuje da se mehanizam razgradnje MCPP primenom  vidljive svetlosti ne odvija posredstvom •OH-radikala, za razliku od onog uz primenu UV zračenja. S obzirom da se katalizator TiO2 Degussa P25 uz primenu vidljive svetlosti nije  pokazao kao naročito efikasan kada je u pitanju razgradnja sva tri herbicida i imajući u vidu da se u poslednje vreme iz razloga praktične primene sve više pribegava procesu dopovanja TiO2 različitim tipovima metala (alkalnih, zemnoalkalnih, prelaznih i dr.) i nemetala (halogenida, halkogenida i dr.), u okviru ove doktorske disertacije je ispitana aktivnost N-TiO2 (sintetisanih mokrim i suvim putem) i TiO2 (rutil) dopovanog sa različitim količinama Fe3+-jona (0,13−1,48 at.%) pri razgradnji herbicida MCPP i MCPA primenom vidljive svetlosti. Pored toga je ispitana efikasnost TiO2 (anataze) takođe dopovanog sa različitim količinama Fe3+-jona (0,71−1,80 at.%) na primeru MCPP.  Poredeći N-TiO2 (sintetisan mokrim putem) i N-TiO2 (sintetisani suvim putem), primećeno je da je u drugom slučaju efikasnost katalizatora veća oko 2 puta. Isto tako je zapažena u slučaju MCPP nešto veća fotokatalitička aktivnost N-TiO2 (sintetisani suvim putem) u poređenju sa TiO2 (anataze). Kada je u pitanju MCPA aktivnost sva tri katalizatora je veoma slična. Pored toga je zapažena veća efikasnost N-TiO2 (sintetisan mokrim putem) u poređenju sa TiO2 Degussa P25 (oko 1,5 puta) i oko 5 puta u odnosu na direktnu fotolizu, dok su N-TiO2 (sintetisani suvim putem) oko 3 puta efikasniji u poređenju sa TiO2 Degussa P25 i oko 10 puta u  poređenju sa direktnom fotolizom. Brzina solarne razgradnje je preko 100 puta manja nego primenom vidljivog i UV zračenja, što je posledica različitih intenziteta pomenutih izvora ozračivanja i različitih uslova pri kojima je vršena razgradnja.  Ustanovljena je optimalna masena koncentracija N-TiO2 (sintetisan mokrim putem) od 4 mg cm−3. Prilikom razgradnje MCPP i MCPA je nađeno da je brzina veća kada se kao katalizator  koristi TiO2 (rutil) u poređenju sa Fe-TiO2 i da sa povećanjem količine Fe3+-jona fotokatalitička aktivnost uglavnom opada. Kada je kao fotokatalizator korišćen TiO2   (anataze) dopovan različitim količinama Fe3+-jona (od 0,71 do 1,80 at.%), razgradnja  MCPP je u svim slučajevima znatno sporija u odnosu na TiO2 (anataze). S obzirom da su prema literaturnim podacima kinetika i mehanizam fotokatalitičke  razgradnje klopiralida nepoznati, ispitana je njegova stabilnost pri različitim eksperimentalnim uslovima. Tokom ispitivanja uticaja pH kako u prisustvu, tako i u odsustvu dnevne svetlosti u intervalu pH od 1,0−9,0, nađeno je da ni u jednom slučaju ne dolazi do razgradnje supstrata u periodu od sedam meseci koliko je proces praćen. Takođe je ispitana kinetika fotokatalitičke razgradnje klopiralida primenom UV i vidljivog zračenja u prisustvu TiO2 Degussa P25, kao i direktna fotoliza primenom oba izvora zračenja. Nađeno je da je brzina fotokatalitičke razgradnje primenom UV zračenja veća oko 5 puta u odnosu na direktnu fotolizu. Za praćenje toka fotokatalitičke razgradnje klopiralida je izabrana pH-vrednost od 3,2. Nadalje je zapaženo da se u ispitivanom opsegu početnih koncentracija supstrata (0,5–3,0 mmol dm−3) kinetika fotokatalitičke razgradnje klopiralida može opisati pseudo-prvim redom. Pri ispitivanju uticaja masene koncentracije katalizatora (0,5–8 mg cm−3) na brzinu razgradnje klopiralida, ustanovljena je optimalna masena koncentracija primenjenog fotokatalizatora od oko 4 mg cm−3. Izračunata ukupna  prividna energija aktivacije iznosi 7,74 kJ mol−1. Pored toga, prisustvo kiseonika ubrzava reakciju 2 puta, dok dodatak elektron-akceptora kao što su (NH4)2S2O8, H2O2 i KBrO3 pokazuje značajan i različit efekat na kinetiku fotokatalitičke razgradnje klopiralida. Pri ispitivanju uticaja etanola, kao hvatača slobodnih radikala, nađeno je da se heterogena fotokataliza odvija uglavnom preko •OH-radikala. Na osnovu LC–MS/MS (ESI+) merenja ustanovljeno je prisustvo nekoliko intermedijera: 3,6-dihlor-piridin-2-ol, 3,6-dihlor hidroksipiridin-2-karboksilna kiselina i 3,3',6,6'-tetrahlor-2,4'-bipiridin-2'-karboksilna kiselina. Na osnovu identifikovanih intermedijera, kao i kinetičkih rezultata, predložen je mogućput mehanizma fotokatalitičke razgradnje klopiralida. Prilikom ispitivanja uticaja strukture molekula na brzinu razgradnje, konstatovano  je da u slučaju klopiralida praktično ne dolazi do fotokatalitičke razgradnje u prisustvu TiO2 (anataze) i N-TiO2 (sintetisani suvim putem) uz primenu vidljive svetlosti, kao i u slučaju TiO2 Degussa P25. Pored toga, primenom TiO2 (rutil) i Fe-TiO2 kao fotokatalizatora, sa povećanjem količine Fe3+-jona od 0,13 do 1,27 at.% raste brzina razgradnje klopiralida, ukazujući da strukturne osobine supstrata utiču na brzinu njihove razgradnje.It is well known that RS-2-(4-chloro-o-tolyloxy)propionic acid (MCPP), (4-chloro-2- methyl-phenoxy)acetic acid (MCPA) and 3,6-dichloropyridine-2-carboxylic  acid (clopyralid) are herbicides of wide activity spectrum. They are soluble in water, hardly biodegradable and, unfortunately, often present in drinking water. Heterogeneous photocatalysis by application of TiO2 and UV radiation proved to be very suitable for their removal from water. However, due toits large energy gap, i.e. 3.2  eV (anatase-form) and 3.0 eV (rutile-form), a very small fraction of sunlight in the near UV range (about 3–4%) is used during photocatalytic process, which is an indication of TiO2 inactivity in the presence of this light source. Some literature data report on the possibility of photodegradation of certain substrates by visible light in the presence of TiO2. MCPP served as substrate for testing TiO2 Degussa P25  photocatalytic activity in the presence of visible light. On the basis of reflection spectra it was established that MCPP adsorbed on TiO2 Degussa P25 was absorbing visible spectrum radiation (λ ≥400 nm). The existence of thus formed  charge-transfer complex was confirmed with FTIR analysis. The efficiency of  TiO2 Degussa P25 with application of visible light was compared to sunlight and UV radiation, as well to directphotolysis in the presence of these light sources. The rate of MCPP photocatalytic degradation by means of visible light is 0.86 μmol dm−3 min−1, which is about 4 times faster than direct photolysis. In addition, the optimal  catalyst concentration of about 8 mg cm−3, much higher than using UV radiation,  was established. The reason is, probably, a different mechanism of  hotodegradation  in the presence of visible and UV irradiation. Namely, the presence of 2-methyl-2-propanol (well-known •OH radical scavenger) has practicallyno effect on the rate of  MCPP photocatalytic degradation using visible light, which points that this degradation mechanism does not involve •OH radicals, in contrast to that established  for UV radiation. Since the catalyst TiO2 Degussa P25 with application of visible light was not very  efficient in degradation of all three herbicidesand in view that nowadays is very  popular doping process of TiO2 with different types of metals (alkali, alkaline-earth, transition, etc.) and non-metals (halogen, chalcogen, etc.), in the scope of this Ph.D.  thesis activities of N-TiO2 (synthesized by wet and dry procedure) and TiO2 (rutile) doped with various amounts of Fe3+ (0.13–1.48 at.%) in degradation processes of  herbicides MCPP and MCPA using visible light were studied. In addition, the efficiency of TiO2 (anatase) doped with various amounts of Fe3+ (0.71–1.80 at.%) was also tested for MCPP degradation. When comparing N-TiO2 (synthesized by wet procedure) and N-TiO2 (dry procedure), it was observed that in the latter case the catalyst efficiency was about two times higher. In this case for MCPP was also observed somewhat higher photocatalytic activity of N-TiO2 (synthesized by dry procedure) in comparison with TiO2. When activities of all three catalysts towards MCPA are compared, the results are very alike. In addition, higher efficiency of N-TiO2  (wet procedure) comparing to TiO2 Degussa P25 (about 1.5 times) and about 5 times in comparison to direct photolysis were recorded, while N-TiO2 (dry procedure) was about 3 times more efficient than TiO2 Degussa P25 and about 10 times in comparison with direct photolysis. The rate of solar degradation is about 100 times lower than by application of UV and visible radiation, as a consequence of various intensities of the mentioned light sources and different conditions of photodegradation. An optimal concentration of N-TiO2 (wet procedure) of 4 mg cm−3  was established. During degradation of MCPP and MCPA it was observed that the rate is higher if TiO2 (rutile) was applied comparing to Fe-TiO2 and with increasing amount of Fe3+ photocatalytic activity mostly decreases. When TiO2 (anatase) doped with various amounts of Fe3+ (0.71 to 1.80 at.%) was applied for MCPP degradation, the process was much slower than with undoped catalyst. Since we have not found relevant literature data on kinetics and mechanism of photocatalytic degradation of clopyralid, its stability in different experimental conditions was tested. In investigating of influences of pH (1.0–9.0) both in presence and in absence of daylight, in no cases decomposition was observed during seven months experiments. Also, the kinetics of photocatalytic degradation of clopyralid using UV and visible irradiation in the presence of TiO2 Degussa P25 and in direct photolysis by application of both irradiation sources was studied. It was found that the  rate of photocatalytic decomposition using UV radiation was 5 times higher comparing to direct photolysis. For clopyralid photocatalytic monitoring a pH value of  3.2 was chosen. In addition, in the investigated concentration range (0.5–3.0 mmol  dm−3) the photocatalytic degradation kinetics of clopyralid in the first stage of the reaction follows approximately a pseudo-first kinetic order. In investigation of influence of catalyst concentration (0.5–8 mg cm−3) on the rate of clopyralid degradation the highest reaction rate was observed at 4 mg cm−3 of catalyst concentration The apparent activation energy of the reaction being 7.74 kJ mol−1. The absence of molecular oxygen resulted in a significant decrease (about 2 times) in the rate of clopyralid photodegradation. The effect of the presence of (NH4)2S2O8, H2O2 and KBrO3, acting as electron acceptors along with molecular oxygen affects clopyralid photocatalytic degradation considerably and indifferent ways. By studying the effect of ethanol as a hydroxyl radical scavenger it was shown that the heterogeneous catalysis takes place mainly via •OH radicals. LC−MS/MS (ESI+) monitoring of the process showed that several pyridine-containing intermediates are formed: 3,6-dichloropyridin-2-ol, 3,6-dichloro hydroxypyridine-2-carboxylic acid and 3,3',6,6'-tetrachloro-2,4'-bipyridine-2-carboxylic acid. Based on the identified intermediates and overall kinetic results, a probable photocatalytic degradation mechanism was proposed.  Finally, in the case of clopyralid it was established that practically no degradation  occurs in the presence of TiO2 (anatase) and N-TiO2 (dry procedure) with visible light  and also with TiO2 Degussa P25. Besides of that, by using TiO2 (rutile) and Fe-TiO2 as photocatalysts it was noted that increasing the concentration of Fe3+ from 0.13 to 1.27 at.% comes to increasing photodegradation rate of clopyralid. Results indicate that differences in molecular structure of chosen compound, influence obtained photocatalytic activity to a great extent