<p>Osnovni cilj istraživanja predstavlja ispitivanje efektivnosti<br />komunikacije privrednih subjekata sa elektronskom upravom,<br />utvrđivanje njihovih potreba i trenutnih prepreka pri upotrebi<br />servisa. Sa praktične tačke gledišta, disertacija predlaže<br />višedimenzionalni model, koji može pomoći kreatorima ekonomske<br />politike da ispitaju koliko su uspešno implementirani servisi<br />elektronske uprave, koji su propusti dosadašnjeg razvoja e-uprave, kao<br />i koje su najefikasnije mere za podsticanje prihvatanja elektronskih<br />javnih servisa od strane poslovnog sektora.</p> / <p>The main objective of the research was to examine the effectiveness of<br />business entities communication with electronic government, the assessment<br />of their needs and the current obstacles to the use of the service. From a<br />practical point of view, the thesis proposes a multi-dimensional model which<br />can help economic policy makers to examine how successfully electronic<br />administration services are implemented, which are failures of the previous<br />development of e-government, as well as which are the most effective<br />measures to encourage the acceptance of electronic public services by the<br />business sector.</p>

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Name="Emphasis"/> <w:LsdException Locked="false" Priority="59" SemiHidden="false" UnhideWhenUsed="false" Name="Table Grid"/> <w:LsdException Locked="false" UnhideWhenUsed="false" Name="Placeholder Text"/> <w:LsdException Locked="false" Priority="1" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="No Spacing"/> <w:LsdException Locked="false" Priority="60" SemiHidden="false" UnhideWhenUsed="false" Name="Light Shading"/> <w:LsdException Locked="false" Priority="61" SemiHidden="false" UnhideWhenUsed="false" Name="Light List"/> <w:LsdException Locked="false" Priority="62" SemiHidden="false" UnhideWhenUsed="false" Name="Light Grid"/> <w:LsdException Locked="false" Priority="63" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Shading 1"/> <w:LsdException Locked="false" Priority="64" SemiHidden="false" UnhideWhenUsed=&q / <p>Cilj &ndash; Cilj disertacije je da se omogući dinamičko prilagođavanje metapodataka koji opisuju obrazovne resurse u digitalnim repozitorijumima.</p><p>Metodologija - Postoji potreba da se u digitalnim repozitorijumima obrazovni resursi opi&scaron;u putem skupa metapodataka koji je specifičan za određenog korisnika ili domen. Obzirom da korisnici ne mogu samostalno da ručno vr&scaron;e izmenu softverske aplikacije, pristup predložen u ovoj disertaciji se zasniva na tehnikama modelom vođenog razvoja softvera, koji treba da omogući prilagođavanje softverske aplikacije programski, bez potrebe za razvojem ili naručivanjem nove aplikacije. Da bi se predloženo re&scaron;enje verifikovalo, sproveden je eksperiment koji evaluira njegove karakteristike.</p><p>Rezultati - U disertaciji je predložena softverska platforma za upravljanje obrazovnim resursima opisanim dinamički pro&scaron;irivim skupom metapodataka. Platforma omogućuje kreiranje modela podataka koji se programski transformi&scaron;u u veb aplikaciju za upravljanje obrazovnim resursima. Na ovaj način, korisnik može da kreira sopstveni model metapodataka koji je odgovarajući u određenom domenu.</p><p>Ograničenja istraživanja/implikacije &ndash; Re&scaron;enje verifikovano od strane korisnicima sa određenim tehničkim znanjem. Potrebno je istražiti prikladnost platforme za domenske eksperte sa ograničenim tehničkim znanjem, koji treba da defini&scaron;u nove skupove metapodataka u svom domenu.</p><p>Praktične implikacije &ndash; Re&scaron;enje se može koristiti u digitalnim repozitorijuma koji skladi&scaron;te raznolike obrazovne resurse. Svaki resurs može biti opisan koristeći metapodatke iz domena kojem resurs pripada.<br />Originalnost/vrednost - Digitalni repozitorijumi standardno opisuju obrazovne resurse koristeći neki generalni skup metapodataka, koji je vi&scaron;e fokusiran na fizičke karakteristike resursa, umesto na njihovo značenje. Predloženo re&scaron;enje uvodi proizvoljnu domenski-zavisnu semantiku u opis resursa, čime se unapređuje njihovo dobavljanje.</p>

<p>Cilj. Cilj disertacije je razvoj pro&scaron;irive softverske platforme za upravljanje kurikulumom u internacionalizovanom visokom obrazovanju koja doprinosi razvoju zajedničkog jezika u istraživanju kurikuluma, a da se pri tome ne ograniče lokalne zajednice prakse istraživanja kurikuluma pozicionirane u nacionalno-specifične obrazovne kontekste, odnosno da se pokaže da je moguće primeniti postojeće međunarodne standarda, pro&scaron;irene eventualnim dodatnim zahtevima, u visoko&scaron;kolskom sistemu Republike Srbije.<br />Metodologija. Kao osnova za modeliranje metapodataka kojima se opisuju kurikulumi u internacionalizovanom visokom obrazovanju kori&scaron;ćeni su međunarodni standardi MLO-AD i MLO ECTS IP/CC za predstavljanje obrazovnih prilika. Za predstavljanje metapodataka kori&scaron;ćene su OWL ontologije. Za razvoj sistema kori&scaron;ćena je iterativna metoda razvoja softvera, a implementacija je izvr&scaron;ena kori&scaron;ćenjem programskih jezika Java i Python, XML tehnologije, tehnologije veb servisa i tehnologije Semantičkog Veba. Verifikacija modela metapodataka i sistema za upravljanje kurikulumom je izvr&scaron;ena na realnom studijskom programu akreditovanom na na Fakultetu tehničkih nauka u Novom Sadu.<br />Rezultati. U ovoj disertaciji ostvareni su sledeći rezultati:<br />Predložen je model podataka za upravljanje kurikulumom u internacionalizovanom visoko&scaron;kolskom obrazovanju baziran na konceptu obrazovne prilike kao osnovne jedinice za upravljanje kurikulumom, uz oslonac na standardne modele metapodataka za predstavljanje obrazovnih prilika u Evropskoj oblasti visokog obrazovanja.<br />Predložena je ma&scaron;inski čitljiva reprezentacija modela putem sintakse dovoljno ekspresivne za implementaciju modela i sama implementacija modela u obliku OWL ontologije.<br />Predložena je formalna, ma&scaron;inski čitljiva reprezentacije obrazovnih ciljeva koja omogućuje proveru konzistentnosti kurikuluma.<br />Predložena je softverska arhitektura platforme čija je prednost mogućnost jednostavnog pro&scaron;irivanja novim servisima, uključujući i integraciju sa drugim sistemima.<br />Ograničenja istraživanja/implikacije. Osnovno ograničenje teorijskog okvira kojim se razvoj platforme pozicionira u internacionalizovano istraživanje kurikuluma je &scaron;to postojeća praksa upravljanja kurikulumom jo&scaron; uvek odstupa od proklamovanih smernica. Implikacija je ograničena mogućnost da korisnici u punoj meri koriste platformu. Ograničenja predloženog modela odnose se na potrebu njegovog pro&scaron;irivanja zarad zadovoljavanja specifičnih potreba krajnjih korisnika. Implikacija je potreba da se ulože dodatni napori za zadovoljavanje specifičnih potreba korisnika. Ograničenja u delu ma&scaron;inski čitljive reprezentacije su direktna posledica postojećih ograničenja tehnologija Semantičkog Veba u domenu semantičke ekspresivnosti i performansi. Implikacije su ograničena mogućnost kontekstualno zavisnog opserviranja kurikuluma i ograničena mogućnost praktičnog kori&scaron;ćenja reprezentacije modela zbog problema performansi aplikacija Semantičkog Veba.<br />Praktične implikacije. Krajnja namena ovog modela je unapređivanje semantičke interoperabilnosti u Areni Evropskog Visoko&scaron;kolskog obrazovanja putem tehničkog mapiranja informacija o kursevima i drugim obrazovnim prilikama na interoperabilnu specifikaciju obrazovnih prilika. Platforma ima sledeće moguće praktične primene:<br />Ogla&scaron;avanje kurseva.<br />Posredovano prijavljivanje (brokerski servis) za uče&scaron;će u obrazovnim prilikama,<br />Poređenje obrazovnih prilika (u odnosu na referentne repere i međusobno),<br />Evaluacija i kontrola kvaliteta akademskih obrazovnih prilika,i<br />Praćenje studentskog postignuća (Transcript of Records, ToR).<br />Originalnost/vrednost. Originalan doprinos nauci je sledeći.<br />Artikulisanje teorijskog okvira istraživanja kojim se razvoj platforme za upravljanje kurikulumom u internacionalizovanom visokom obrazovanju pozicionira u internacionalizovano istraživanje kurikuluma i koncept obrazovne prilike usvaja kao osnovna jedinica za upravljanje kurikulumom.<br />Predlog modela podataka za upravljanje kurikulumom u internacionalizovanom visoko&scaron;kolskom obrazovanju baziran na konceptu obrazovne prilike kao osnovne jedinice za upravljanje kurikulumom, uz oslonac na standardne modele metapodataka za predstavljanje obrazovnih prilika u Evropskoj oblasti visokog obrazovanja.<br />Predlog ma&scaron;inski čitljive reprezentacije modela putem sintakse dovoljno ekspresivne za implementaciju modela i sama implementacija modela u obliku OWL ontologije.<br />Predlog formalne, ma&scaron;inski čitljive reprezentacije obrazovnih ciljeva koja omogućuje proveru konzistentnosti kurikuluma.<br />Predlog softverske arhitekture platforme baziran na predloženom modelu i tehnologijama Semantičkog Veba.<br />Prototipska implementacija i njena primena na studiji slučaja realnog akreditovanog studijskog programa predstavljaju verifikaciju i potvrdu praktične vrednosti predloženog modela i softverske arhitekture platforme.</p> / <p>Purpose &ndash; The aim of the dissertation is the development of extensible software platform for managing internationalized curriculum in higher education. The platform contributes to the development of shared curriculum study language which does not limit the local educational practices. The solution proposed in this dissertation is in accordance with the national- specific educational context as well as existing international standards and is fully applicant to the higher education system of the Republic of Serbia .<br />Design/methodology/approach &ndash; The platform is based upon the international standards MLO -AD and MLO ECTS IP / CC that represent learning opportunities. The standards are implemented as OWL ontologies. The system was developed by using iterative software development methods , and the implementation is done by using Java and Python programming language , XML technologies, Web services and Semantic Web technologies. The verification of the metadata model and the system in whole is carried out on an accredited degree program in the Faculty of Technical Sciences in Novi Sad.<br />Findings. In this dissertation, following results were achieved:<br />&bull; The data model for managing curriculum in internationalized higher education based upon the concept of learning opportunities and relying on the standardized metadata model for representing the learning opportunities in the European higher education area was proposed.<br />&bull; The machine readable representation of the model was adopted. The syntax is expressive enough for the implementation of the model. The model was implemented as a set OWL ontologies.<br />&bull; The formal, machine readable representation of educational objectives which allows formal curriculum evaluation and consistency check is proposed.<br />&bull; The extensible platform for managing curriculum in the internationalized higher education is proposed.<br />Research limitations / implications &ndash; The main limitation of the theoretical framework that is the basis of the platform is that existing educational practice often is not consistent with the contemporary findings of the curriculum theory. The implication of this fact is limited ability for users to make full use of the platform. Limitations of the proposed model are related to the need for its extensions that should satisfy the specific needs of the end users. The implication of this limit is the need to make additional efforts to meet the specific needs of the users. Limitations concerning the machine-readable representations of the model are a direct consequence of the limitations of existing Semantic Web technologies in the domain of semantic expressiveness and performance. The implications are limited possibility of contextually dependent observation of the curriculum and the limited possibility of practical use of the model representation due to the performance problem present in the Semantic Web applications.<br />The practical implications. The main purpose of this model is to improve semantic interoperability in the European higher education area through the mapping of the information on courses and other educational opportunities onto the interoperable specification of learning opportunities . The platform has the following practical applications:<br />&bull; Course advertising.<br />&bull; Mediated enrollment (brokerage services) to learning opportunities,<br />&bull; Comparison of learning opportunities (relative to the reference benchmarks and each other),<br />&bull; Evaluation and quality control of academic learning opportunities , and<br />&bull; Monitoring of student achievement (Transcript of Records, ToR) .<br />Originality/value &ndash;The scientific contribution of this dissertation are following:<br />&bull; Articulating the theoretical framework necessary for the development of the platform for curriculum management in internationalized higher education.<br />&bull; Development of the data model based upon the concept of the learning opportunities.<br />&bull; Proposing the machine-readable representation of the model through syntax expressive enough for the implementation of the model and the actual implementation of the model in the form of OWL ontologies.<br />&bull; Proposing a formal, machine-readable representation of educational objectives, which allows curriculum consistency check.<br />&bull; Proposing the software platform based on the proposed model and the Semantic Web technologies.<br />The proposed platform was verified by implementing a prototype and applying it to the case study of an accredited degree program held at the Faculty of Novi Sad.</p> / null

<p>Značajan porast prevalence dentalnih erozija u savremenom dru&scaron;tvu, zahteva sve vi&scaron;e pažnje ka&nbsp; istraživanju njihove etiologije i preventivnih mera koje se mogu preduzeti. Cilj ove studije bio je da se ispita erozivni potencijal gaziranih napitaka i njihov uticaj na zubna tkiva, tokom različitih vremenskih intervala.<br />Stepen kiselosti izražen pH vrednostima za svaki ispitivani napitak (gaziranu vodu &bdquo;Knjaz Milo&scaron;&ldquo;, Coca-Cola-u i Schweppes Bitter Lemon), određen je odmah po otvaranju ambalaže sa napitkom, nakon 5 i 60 minuta kao i nakon 12 i 24 sata od potapanja zubnih uzoraka. U ovoj studiji posmatrane su mikroskopske promene proučavanjem skening elektronske mikrofotografije spolja&scaron;nje povr&scaron;ine gleđi, kao i uzdužni presek gleđi i dentina zuba nakon izlaganja gore navedenim napicima 5 i 60 minuta,12 i 24 sata kao i 7 i 30 dana, ali i makroskopske promene boje i strukture gleđi u svim navedenim vremenskim intervalima. Za određivanje stepena nastalih mikroskopskih i makroskopskih promena primenjene su individualno prilagođene skale.<br />Početna pH vrednost svih ispitivanih napitaka je niža od kritične pH vrednosti za demineralizaciju gleđi. Sa porastom vremena od potapanja zubnih uzoraka u napitke, njihova pH vrednost značajno raste. Na SEM mikrofotografijama gleđi i dentina se uočavaju promene u morfologiji, čiji intenzitet zavisi od vrste napitka i vremena koje je uzorak u njemu proveo. Centralni tip demineralizacije prisutan je kod uzoraka potopljenih u kiselu vodu i Coca Cola napitak a periferni kod Schweppes Bitter Lemon. Intenzitet promena zubnih tkiva raste u funkciji vremena, ali statistički značajna razlika ne postoji između svih vremenskih intervala. Zubi koji su bili izloženi delovanju gazirane vode &bdquo;Knjaz Milo&scaron;&ldquo; ne pokazuju izmene u makroskopskom izgledu, za razliku od zuba koji su tretirani Coca-Cola-om i Schweppes Bitter Lemon-om čiji intenzitet izmenjenosti raste u funkciji vremena, s tim da je statitički značajna razlika prisutna između pojedinih vremenskih intervala. S obzirom na erozivni potencijal i promene koje gazirani napitci izazivaju u in vitro условима, potrebno je preduzeti odgovarajuće preventivne mere kako bi se smanjio njihov uticaj na zube u in vivo uslovima.</p> / <p>Značajan porast prevalence dentalnih erozija u savremenom dru&scaron;tvu, zahteva sve vi&scaron;e pažnje ka&nbsp; istraživanju njihove etiologije i preventivnih mera koje se mogu preduzeti. Cilj ove studije bio je da se ispita erozivni potencijal gaziranih napitaka i njihov uticaj na zubna tkiva, tokom različitih vremenskih intervala.<br />Stepen kiselosti izražen pH vrednostima za svaki ispitivani napitak (gaziranu vodu &bdquo;Knjaz Milo&scaron;&ldquo;, Coca-Cola-u i Schweppes Bitter Lemon), određen je odmah po otvaranju ambalaže sa napitkom, nakon 5 i 60 minuta kao i nakon 12 i 24 sata od potapanja zubnih uzoraka. U ovoj studiji posmatrane su mikroskopske promene proučavanjem skening elektronske mikrofotografije spolja&scaron;nje povr&scaron;ine gleđi, kao i uzdužni presek gleđi i dentina zuba nakon izlaganja gore navedenim napicima 5 i 60 minuta,12 i 24 sata kao i 7 i 30 dana, ali i makroskopske promene boje i strukture gleđi u svim navedenim vremenskim intervalima. Za određivanje stepena nastalih mikroskopskih i makroskopskih promena primenjene su individualno prilagođene skale.<br />Početna pH vrednost svih ispitivanih napitaka je niža od kritične pH vrednosti za demineralizaciju gleđi. Sa porastom vremena od potapanja zubnih uzoraka u napitke, njihova pH vrednost značajno raste. Na SEM mikrofotografijama gleđi i dentina se uočavaju promene u morfologiji, čiji intenzitet zavisi od vrste napitka i vremena koje je uzorak u njemu proveo. Centralni tip demineralizacije prisutan je kod uzoraka potopljenih u kiselu vodu i Coca Cola napitak a periferni kod Schweppes Bitter Lemon. Intenzitet promena zubnih tkiva raste u funkciji vremena, ali statistički značajna razlika ne postoji između svih vremenskih intervala. Zubi koji su bili izloženi delovanju gazirane vode &bdquo;Knjaz Milo&scaron;&ldquo; ne pokazuju izmene u makroskopskom izgledu, za razliku od zuba koji su tretirani Coca-Cola-om i Schweppes Bitter Lemon-om čiji intenzitet izmenjenosti raste u funkciji vremena, s tim da je statitički značajna razlika prisutna između pojedinih vremenskih intervala. S obzirom na erozivni potencijal i promene koje gazirani napitci izazivaju u in vitro uslovima, potrebno je preduzeti odgovarajuće preventivne mere kako bi se smanjio njihov uticaj na zube u in vivo uslovima.</p> / <p>Due to the fact that prevalence of dental erosion significantly increased in modern society, it is important to investigate its etiological factors and all available preventive measures. The aim of this study was to investigate erosive potential of carbonated beverages and their influence on dental hard tissues, during different intervals.<br />The acidity or pH level was measured for each beverage (carbonated water &bdquo;Knjaz Milos&ldquo;, Coca-cola and Schweppes Bitter Lemon), on opening of the bottle, after 5 minutes and 60 minutes, and after 12 hours and 24 hours immersion of tooth samples in adequate beverage. In this study, microscopic changes of dental tissues were examined using a scanning electron microphotography of outer surface of enamel and longitudinal section of enamel and dentin, after exposure to beverages during 5 and 60 minutes, 12 and 24 hours, and 7 and 30 days, as well as macroscopic changes of tooth color and structure at same intervals. Individually adopted scales were used for grading of the severity of microscopic and macroscopic changes.<br />Initiated pH value of each tested beverage was lower than critical pH for enamel demineralisation. SEM images of enamel and dentin showed different morphology changes, which intensivity depended on type of beverages and time that sample were stored. Central type of demineralisation was visible on samples treated with carbonated water and Coca-Cola, while peripheral type of demineralisation was detected on samples treated with Schweppes Bitter Lemon. The intensity of alterations of dental tissues increased during time, but there was not statistically significant difference between all intervals. There wasn&rsquo;t detected macroscopic changes on teeth stored in carbonated water, while teeth treated with Coca-Cola and Schweppes Bitter Lemon showed changes which intensity increased during time, but statistically significant difference between all intervals wasn&rsquo;t detected. Due to erosive potential and changes influenced by carbonated beverages in vitro, preventive measures are necessary for reducing their effect on teeth in vivo.</p>

<p>U ovom radu prikazani su rezultati ispitivanja termičkih, mehaničkih, električnih i optičkih karakteristika kvazibinarnih halkogenida iz sistema Bi-As2S3. Na osnovu termičkih merenja analizirana je kinetika kristalizacionih i predkristalizacionih procesa i utvrđen je mehanizam dekompozicije za različite sastave dobijenih stakala. Primenom impedansne spektroskopije kvantitativno su ocenjeni doprinosi relaksacionih procesa na pojedinim temperaturama u ukupnoj polaraziciji za stakla sa 5 i 7 at.% Bi. Na osnovu merenja Raman spektroskopije identifikovane su nastale strukturne jedinice i konstatovana pojava nanofazne separacije u staklima sa 1.5 i 3 at.% Bi. Mehanička merenja ispitivanih halkogenida različitog sastava ukazala su na povećanje Vickers-ove tvrdoće sa povećanjem udela primesnih atoma. Na osnovu procenjene vrednosti modula elastičnosti ustanovljeno je da uzorak sa 5 at.% Bi odlikuje najgu&scaron;će atomsko pakovanje. Merenja električnih karakteristika u jednosmernom režimu (DC) pokazala su da je udeo lokalizovanih stanja u ukupnom mehanizmu provođenja značajan samo za manje koncentracije primesnih atoma, a da za veće koncentracije dominantan faktor postaju preskoci između delokalizovanih stanja. Skok u provodljivosti za nekoliko redova veličine kod sastava sa složenijom strukturom protumačen je kao posledica fazne separacije. Rezultati&nbsp; ACmerenja dobijeni za sastav sa 5 at.% Bi ukazali su da je u mernom frekventnom intervalu i dalje dominantan mehanizam termičke aktivacije nosilaca naelektrisanja. Kod sastava sa maksimalnim sadržajem Bi uočena je promena provodljivosti u funkciji frekvencije na svim temperaturama, a dobijeni rezultati su u skladu sa postavkama modela korelisanih preskoka barijere (CHB model).</p> / <p>This paper presents the results of investigation ofthermal, mechanical, electrical and optical propertiesof quasibinar chalcogenides from the system Bi-As2S3.&nbsp;Kinetics analysis of softening and crystallizationprocesses was done on the basis of thermalmeasurements, as well the analysis of decompositionmechanism for different compositions of obtainedglasses. The application of impedance spectroscopy enabled quantitative description of relaxation process contributions at selected temperatures in the overallpolarization for the samples with 5 and 7 at.% Bi.&nbsp;Based on measurements of Raman spectroscopy identification of structural units in the investigated chalcogenides was made, as well as the appearance of&nbsp;nano-scale phase separation in the glasses with 1.5 and 3 at.% Bi. Mechanical measurements pointed to the increase of the Vickers hardness with increase of&nbsp;doping atoms content. &nbsp;Based on the estimated value of the modulus of elasticity it was found that the sample &nbsp;with 5 at.% Bi is characterized by the densest atomic&nbsp;arrangement. Measurements of the electrical properties in dc regime (DC) pointed out that the share of localized states in the whole mechanism of conduction&nbsp;is significant only for the smaller concentrations of doping atoms. For the samples with higher concentrations dominant &nbsp;factor in conductivity are transitions between delocalized states. The jump in conductivity by few orders of magnitude, noticed for&nbsp;the compound with heterogeneous structure was interpreted as a consequence of micro-scale phase&nbsp; separation. Results of&nbsp; ACmeasurements for the&nbsp; composition with 5 at.% Bi showed that the mechanism of thermal activation of charge carriers is&nbsp;still dominant in the measured frequency range. For&nbsp;&nbsp; the composition with the maximum content of Bi changes in conductivity versus frequency were observed at all temperatures, and the results were interpreted in accordance with the model of correlated hopping over the barrier (CHB).</p>

<p>Ugljenične nanocevi (UNC) imaju sve veću primenu u elektronici, kompjuterskoj i optičkoj industriji, kao i u biomedicini. Dok proizvodnja jednoslojnih UNC nanocevi beleži sve veći rast poslednjih godina, rizik koji nosi izlaganje ovom nanomaterijalu ostaje nerazja&scaron;njen. Oskudni i često kontradiktorni podaci o toksičnim efektima jednoslojnih UNC ukazuju na potrebu za daljim ispitivanjima. U na&scaron;im istraživanjima ispitivane su promene u ćelijskom odgovoru kao i morfolo&scaron;ke promene nakon delovanja jednoslojnih ugljeničnih nanocevi na ćelijskoj liniji humanih fetalnih fibroblasta pluća MRC-5 i ćelijskoj liniji humanog adenokarcinoma pluća A549. U ovoj studiji kori&scaron;ćene su jednoslojne ugljenične nanocevi koje su sadržale rezidualne nečistoće poput gvožđa. Citotoksičnost jednoslojnih UNC (engl. single-walled carbon nanotubes &ndash; SWCNT) je ispitivana kolorimetrijskim MTT testom. Tokom 24 i 48h niske koncentracije jednoslojnih ugljeničnih nanocevi (&lt;250 &mu;g/mL) pokazale su nisku toksičnost na proliferaciju i vijabilnost u obe ispitivane ćelijske linije. Ipak, pri visokim koncentracijama UNC (250-750 &mu;g/mL) antiproliferativni efekat je bio blizu IC50 vrednostima. Na osnovu rezultata dobijenih MTT testom može se zaključiti da su maligne A549 ćelije osetljivije na delovanje jednoslojnih UNC u odnosu na normalne MRC-5 ćelije. Kombinacija ugljeničnih nanocevi sa prirodnim polifenolima (resveratrolom i proantocijanidolima) nije značajno uticala na citotoksičnost u MRC-5 ćelijama, za razliku od A549 ćelija gde je tretman kombinacijama umanjio toksičnost ugljeničnih nanocevi. Transmisionom elektronskom mikroskopijom ispitivan je efekat jednoslojnih ugljeničnih nanocevi na ćelijsku morfologiju i preživljavanje. Intracelularni agregati ugljeničnih nanocevi primećeni su u obe ćelijske linije, čime je potvrđeno da ugljenične nanocevi ulaze u ćelije. Imajući u vidu da nanomaterijali poput ugljeničnih nanocevi indukuju oksidativni stres i njime posredovanu apoptozu, na protočnom citometru je određivano prisustvo ćelija u apoptozi i nekrozi. Tretman ćelija sa jednoslojnim ugljeničnim nanocevima nije doveo do značajnog porasta broja apoptotskih ili nekrotičnih ćelija, &scaron;to ide u prilog niskoj toksičnosti ovog nanomaterijala, odnosno ukazuje na alternativne mehanizme toksičnosti. Međutim kombinacija jednoslojnih ugljeničnih nanocevi sa antioksidantima, resveratrolom i proantocijanidolima indukuje veći procenat apoptoze i nekroze u odnosu na tretman samo sa nanocevima. Promene u ekspresiji gena praćene su lančanom reakcijom polimeraza (PCR). Komparativna analiza rezultata genske ekspresije MRC-5 i A549<br />ćelija nakon tretmana sa jednoslojnim ugljeničnim nanocevima pojedinačno i u kombinaciji sa antioksidantima ukazala je na kompleksnost i raznolikost biolo&scaron;kog odgovora ispitivanih ćelija. U na&scaron;em istraživanju ispitivana je i promena aktivnosti enzima antioksidativne za&scaron;tite i količine glutationa u ćeliji. Primena jednoslojnih ugljeničnih nanocevi u MRC-5 ćelijama dovodi po smanjenja specifične aktivnosti enzima SOD i GR, povećava specifičnu aktivnost GPx i ne utiče na promenu specifične aktivnosti GST i količine glutationa u ćeliji Primena jednoslojnih ugljeničnih nanocevi u A549 ćelijama dovodi po smanjenja specifične aktivnosti enzima SOD, ne utiče na promenu specifične aktivnost enzima GR, GST i GPx, i dovodi do povećanja količine glutationa u ćeliji. Ćelijska vijabilnost, morfolo&scaron;ke promene, redoks homeostaza i ekspresija ispitivanih gena bile su promenjene nakon tretmana sa jednoslojnim ugljeničnim nanocevima. Iako su dobijeni rezultati značajni za procenu toksičnosti ugljeničnih nanocevi, neophodna su dalja istraživanja koja treba da doprinesu boljem razumevanju toksičnih efekata ugljeničnih nanocevi.</p> / <p>Carbon nanotubes are being actively introduced in electronics, computer science, and optics as well as for various biomedical applications. While production of single-walled carbon nanotubes (SWCNT) has escalated in recent years, the knowledge on risk associated with exposure remains unclear. Contradictory data on the toxic effects of single-walled carbon nanotubes highlights the urgent need for further studies. In this study we investigated the alterations in cellular response along with morphological changes induced by single-walled carbon nanotubes in human lung fibroblast cell line MRC-5 and adenocarcinoma human alveolar basal epithelial cells A549. In this study we used SWCNT containing large amounts of residual metallic impurities such is iron, and the iron concentration increased in dose dependent manner in cells exposed to SWCNT. Cytotoxicity was evaluated by MTT assay and SWCNT showed little cytotoxic effect on the proliferation and viability of two cell lines tested at the concentrations used (&lt;250 &mu;g/mL) within 24 and 48h. However exposing both cell lines to high concentrations (250-750 &mu;g/mL) resulted in near IC50 values. Based on MTT test SWCNT were more cytotoxic to A549 cell line. Cytotoxicity of SWCNT in combination with natural polyphenols (resveratrol and proanthocyanidins) did not noticeably affect the cytotoxicity of SWCNT to MRC-5 cells. However introduction of polyphenols did reduce the cytotoxicity of SWCNT to A549 cells. Transmission electron microscopy was used to complement cytotoxicity assays and to investigate the pathological effect of internalized SWCNT on cell morphology and survival. Intracellular bundles of CNTs, possibly aggregated/agglomerated were observed in both cell lines, confirming internalization after 24h exposure. Since nanoparticles like carbon nanotubes are toxic mainly because they cause oxidative stress, often associated with an increased apoptosis we checked for apoptotic and necrotic cells using flow cytometry. Incubation with SWCNT did not result in pronounced apoptosis or necrosis supporting its low toxicity and possibly alternative mechanism of cell damage. However incubation with SWCNT in combination with resveratrol and proanthocyanidins induced higher levels of both apoptosis and necrosis than SWCNT alone. Changes in gene expression following exposure to SWCNT were evaluated by polymerase chain reaction PCR array which indicated complex and diverse change in expression of genes involved in apoptosis, cell proliferation and oxidative stress. Finally we investigated the modulation of the antioxidant enzyme system and the changes in the cytosolic levels of GSH. SWCNT reduced the specific activity of SOD and GR enzymes, increased GPx activity. No changes in intracellular levels of GSH were observed in MRC-5 cell line. Same treatment in A549 cell reduced the specific activity of SOD, had no effect on GR, GST and GPx activity, but increased intracellular levels of GSH. Cell viability, morphologic changes, redox homeostasis and gene expression were affected by the presence of SWCNT. Although our findings are useful in predicting human response against SWCNT exposure, further study is needed for better understanding of the effects of SWCNT.</p>

<p>Predmet istraživanja ove doktorske disertacije su bila halkogenidna stakla iz sistema Ag_x(As₄₀S₃₀Se₃₀)_100&ndash;x (x = 0, 0.5, 1, 2, 3, 4, 5, 10, 12, 13, 15 at. % Ag) &ndash; 3D forma i tanki filmovi preparirani iz prethodno sintetisanih stakala (x &le; 5 at. % Ag) &ndash; 2D forma.<br />Utvrđena je oblasti amorfnosti u faznom dijagramu po odabranom preseku.&nbsp; Ispitivan je uticaj procentualnog udela srebra&nbsp; na&nbsp; fizičke&nbsp; karakteristike sintetisanih stakala i prepariranih tankih filmova koje su&nbsp; od&nbsp; značaja&nbsp; za&nbsp; primenu&nbsp; ovakvih&nbsp; materijala.<br />Izvr&scaron;ena je karakterizacija električnih,&nbsp; optičkih, strukturnih&nbsp; i&nbsp; termičkih&nbsp; osobina&nbsp; na&nbsp; osnovu&nbsp; kojih&nbsp; su izvedeni&nbsp; zaključci&nbsp; o&nbsp; uticaju&nbsp; i&nbsp; modifikaciji&nbsp; strukture As₄₀S₃₀Se₃₀halkogenidne matrice usled inkorporacije atoma srebra. Strukturna analiza ispitivanih sastava je potvrdila homogenost uzoraka sa manjom koncentracijom srebra (x &le; 5 at. %&nbsp; Ag), dok je&nbsp; kod uzoraka sa većim procentualnim udelom ovog metala (x = 10, 13, 15 at. % Ag) pokazano da postoji fazna separacija. Kod sastava sa x = 13 i 15 at. % Ag potvrđena&nbsp; je&nbsp; prisutnost kristalnih centara AgAsSe_2. Na osnovu rezultata dobijenih DSC tehnikom, pokazano je da pri zagrevanju balk uzoraka dolazi do delimične kristalizacije koja se odvija zapreminski sa dvodimenzionalnim&nbsp; i&nbsp; trodimenzionalnim rastomkristalnih centara. Optička i spektralna ispitivanja su pokazala&nbsp; da uvođenje&nbsp; Ag&nbsp; u&nbsp; matricu&nbsp; stakla As₄₀S₃₀Se₃₀&nbsp; dovodi&nbsp; do&nbsp; smanjenja&nbsp; &scaron;irine&nbsp; optički zabranjene zone i kod 3D i 2D uzoraka, kao i da svi sastavi ispoljavaju normalan oblik disperzije indeksa prelamanja. Takođe, rezultati Raman&nbsp; spektroskopije su ukazali&nbsp; na&nbsp; činjenicu&nbsp; da&nbsp; inkorporacija&nbsp; srebra&nbsp; u strukturnu&nbsp; mrežu&nbsp; ispitivanih&nbsp; stakala&nbsp; utiče&nbsp; na formiranje Ag&ndash;(S,Se)&ndash;As veza, odnosno uzrokuje formiranje novih strukturnih jedinica koje bi mogle uticati na provodljivost ovih sastava.&nbsp; Merenja električnih karakteristika 3D uzoraka izvr&scaron;ena su u jednosmernom i naizmeničnom režimu i pokazano je da&nbsp; koncentracija&nbsp; srebra&nbsp; ima&nbsp; značajan&nbsp; uticaj&nbsp; na električne&nbsp; osobine.&nbsp; Utvrđeni&nbsp; su&nbsp; različiti&nbsp; mehanizmi odgovorni za transport&nbsp; nosilaca naelektrisanja zavisno od&nbsp; koncentracije dopanta.&nbsp; Kompleksni impedansni spektri svih sastava&nbsp; su&nbsp; ukazali&nbsp; na prisustvo temperaturske zavisnosti procesa relaksacije, na ne idealan Debye&ndash;vski tip relaksacije, kao i negativni temperaturski koeficijent otpornosti koji je karakterističan za poluprovodnike.</p> / <p>The subject of this dissertation are chalcogenide&nbsp; glasses from the system Agx(As₄₀S₃₀Se₃₀)_100&ndash;x (x = 0, 0.5, 1, 2, 3, 4, 5, 10, 12, 13, 15 at. % Ag) &ndash; 3D form and thin films prepared from previously synthesised&nbsp; glasses (x &le; 5 at. % Ag) &ndash; 2D form. The amorphous&nbsp; area in the phase diagram was determined by the&nbsp; selected&nbsp;&nbsp;&nbsp; tie&ndash; line. The influence of the silver&nbsp; percentage on the physical characteristics of the&nbsp; synthesized glasses and prepared thin films was&nbsp; investigated due to the importance of such materials&nbsp; for the application. Characterization of electrical, optical, structural and thermal properties has been performed, based on which conclusions on theinfluence and structure modification of the As₄₀S₃₀Se₃₀&nbsp; chalcogenide&nbsp; matrix due to the&nbsp; incorporation of silver atoms have been derived. Structural analysis of the investigated samples confirmed the homogeneity of samples with a lower silver concentration (x&nbsp; &le;&nbsp; 5&nbsp; at.%&nbsp; Ag),&nbsp; while&nbsp; in samples with a higher percentage content of&nbsp; this metal (x = 10, 13, 15 at.% Ag) it was shown that&nbsp; there was a phase separation. The presence of crystal&nbsp; centers AgAsSe₂ was confirmed in the samples with x = 13 and 15 at. % Ag. Based on the results obtained with the DSC technique, it has been shown that by heating the samples, partial crystallization takes place voluminously, with two&ndash;dimensional and three&ndash;dimensional growth of crystalline centers.&nbsp; Opticaland spectral investigations have shown that the introduction of Ag into the glass matrix As₄₀S₃₀Se₃₀ leads to a reduction in the optical band gap in both 3D and 2D samples, and that all compositions exhibit a normal dispersion of index of&nbsp; refraction. Also, the Raman spectroscopy results pointed to the fact that the incorporation of silver into the structural network of the investigated samples influences the formation of&nbsp; Ag&ndash;(S,Se)&ndash;As structures that is, causes the formation of new structural units that could affect the conductivity of these compositions. Measurements of the electrical characteristics of the 3D samples were performed in&nbsp; DC and AC regime and it was shown that silver concentration has a significant effect on electrical properties. Different mechanisms that are responsible for the transport of charge carriers depending on dopant concentration were determined. The complex&nbsp; impedance spectra of all compositions indicated the presence of the temperature dependence of the relaxation process, the non&ndash;Debye relaxation and the negative temperature coefficient of resistance which is characteristic of the semiconductors.</p>