THE INFLUENCE OF TEXT PREPROCESSING METHODS AND TOOLS ON CALCULATING TEXT SIMILARITY

Text mining to a great extent depends on the various text preprocessing techniques. The preprocessing methods and tools which are used to prepare texts for further mining can be divided into those which are and those which are not language-dependent. The subject matter of this research was the analysis of the influence of these methods and tools on further text mining. We first focused on the analysis of the influence on the reduction of the vector space model for the multidimensional represen-tation of text documents. We then analyzed the influence on calculating text similarity, which is the focus of this research. The conclusion we reached is that the implemen-tation of various text preprocessing methods in the Serbian language, which are used for the reduction of the vector space model for the multidimensional representation of text document, achieves the required results. But, the implementation of various text preprocessing methods specific to the Serbian language for the purpose of calculating text similarity can lead to great differences in the results

Use of Internet resources and IT tools and characteristics of higher education institutions in Serbia

The purpose of this paper is to determine whether there is a statistically significant influence of characteristics of higher education institutions and scientific fields in which their study programs are accredited, on use of Internet resources and IT tools. The term 'use of Internet resources and IT tools' here refers to enhancing students' skills in use of internet resources, services and technologies on Internet, thus enabling them to create and place new content, services and technologies on the internet. This paper is based on data collected from 196 higher education institutions from Serbia, by a survey questionnaire. The research described in the paper was conducted in 2014. Data processing included a descriptive and correlative analysis. Based on this research, it can be concluded that there is a statistically significant influence of characteristics of higher education institutions on use of Internet resources and IT tools. Detailed research of the content of courses in higher education institutions that deal with internet and technologies surpasses the scope of this research and can be included in future research. This paper presents a new approach in research of influence of higher education institutions and their scientific fields' characteristics on use of Internet resources and IT tools in higher education. The results of this research can be used to improve educational strategies aiming to incorporate the internet use into the curricula of study programs in higher education institutions

Biospecijacija itrijum(III)-jona i njegovih radiofarmaceutika

Radiofarmaceutici bazirani na različitim molekulima obeleženimitrijumom-90, se koriste pri tretmanu neoperativnih vrsta tumora, kao i u radijacionoj sinovektomiji. Veliko interesovanje za korišćenje 90Y u terapeutske svrhe potiče zbog njegovih nuklearnih karakteristika (t1/2=64,1, Eβ,max= 2,3 MeV,bez emisije zračenja). Dostupnost 90Y sa vrlo niskom radiohemijskom kontaminacijom je od suštinske važnosti u terapeutskoj primeni.Postojanje dugoživućeg pretka 90Sr sa vremenom poluživota od 28,9 godina i kratkoživućeg potomka 90Y nam omogućavaju formiranje generatorskog sistema. Iako postoje nekoliko vrsta generatora, prema literaturnim podacima, elektrohemijski generatori i generatori zasnovani na tečnim membranama imaju najveću perspektivu.Membranska ekstrakcija se takođe naziva i pertrakcija i bazirana je natrofaznom sistemu sa organskom fazom (tečna membrana) koja se nalazi između dve vodene faze i predstavlja alternativnu metodu klasičnoj tečno-tečnoj ekstrakciji. Prema literaturnim podacima, koristi se za razdvajanje širokog opsega rastvorenih supstanci uključujući biološke molekule, metalne jone, organske zagađivače i radionuklide.Elektrohemijska metoda je predložena kao rešenje pri separaciji 86Y od 86Sr i dobijanje 86Y koji služi pri pozitronsko emisionoj tomografiji (PET).Literaturni podaci pokazuju da elektrohemijska separacija predstavlja dobro rešenje jer omogućava veliku efikasnost uz minimalnu kontaminaciju okolnog prostora.Radiofarmaceutici koji se koriste u terapiji su u hemijskom smislukompleksna jedinjenja u kojima se kao centralni joni javljaju radioaktivni izotopi metala sa ili raspadom, dok su ligandi organski molekuli koji su sposobni da stvaraju helate. Ovi molekuli pored toga što su helatori za radiometal imaju i ulogu da se vežu za biomolekul. Zbog toga se i nazivaju bifunkcionalni helatori. Najpoznatiji i do sada najviše korišćeni bifunkcionalni helatori u radiohemiji itrijuma su: 1,4,7,10-tetraazociklododekan-1,4,7,10-tetraacetatna kiselina (DOTA) i dietilentriamin-pentasirćetna kiselina (DTPA).Klinička ispitivanja pokazuju da je eliminacija radiofarmaceutika izorganizma uglavnom brza i potpuna. Smatra se i da je metabolička transformacija radiofarmaceutika uglavnom minimalna. Međutim, u određenim uslovima može doći do ispoljavanja toksičnih efekata itrijuma i to kada je eliminacija radiofarmaceutika sprečena ili produžena i kada dolazi do disocijacije radiofarmaceutika. Tada se itrijum raspodeljuje između različitih liganada krvne plazme, prvenstveno, fosfata, karbonata i hidroksida. Biospecijacijazavisi ne samo od prirode radiofarmaceutika već i od prisustva drugihpotencijalnih liganada u krvnoj plazmi kao i neorganskih jona. Premaliteraturnim podacima specijacija i biodistribucija Y(III)-jona u humanoj plazmi, su proučavane u prisustvu ograničenog broja liganada, tako da postoji potreba da se proširi broj liganada koji se koristi prilikom ispitivanja. Tako je, pored već navedenih bifunkcionalnih helatora, u istraživanje uključen i ciprofloksacin, koji predstavlja četvrtu generaciju hinolona aktivnih na Gram-pozitivne bakterije i atipične patogene koji su uzročnici infekcija respiratornog trakta. Kako se Y(III)-jon u organizam unosi kompleksiran ligandima DTPA i DOTA koji se koriste u nuklearnoj medicini potrebno je i njih uključiti prilikom proračuna raspodele ovog jona u humanoj plazmi.Smatra se da je Y(III)-jon u organizmu uglavnom prisutan u obliku svojih hidrolitičkih kompleksa. Odavde može da se zaključi da interakcija Y(III)-jona i liganada u biološkim uslovima predstavlja interakcije sa hidrolitičkim kompleksima itrijuma.U prethodnih trideset godina, hidroliza itrijuma je proučavana povremeno pomoću različitih metoda ali nikada nije sistematski istraženo forimiranje hidrolitičkim kompleksa itrijuma. U literaturi mogu da se nađu pojedinačna ispitivanja hidrolize itrijuma ili termogravimetrijska analiza taloga itrijum-hidroksida, ali ne i podaci o ispitivanju na masenom spektrometru.Potenciometrijske metode daju najkorisnije informacije o vrstamahidrolitičkih komleksa, kao i o njihovim konstantama stabilnosti. Masena spektrometrija nam takođe može dati dosta podataka o vrstama hidrolitičkih kompleksa koje mogu da se jave u rastvorima.Stabilnost komleksa itrijuma sa DTPA, DOTA i ciprofloksacinom se možeodređivati potenciometrijski i masenospektrometrijskim merenjima.Cilj istraživanja ove doktorske teze predstavlja iznalaženje hidrolitičkih vrsta i određivanje njihovih konstati u sistemima koji su kompatibilni sa humanom krvnom plazmom (vodeni rastovor 0,15 mol dm-3 NaCl na 310,0 K). Takođe određivanje konstanti stabilnosti itrijuma sa DTPA i ciprofloksacinom omogućava dobijanje podataka koji se koriste pri specijaciji i određivanju biodistribucije Y(III)-jona u humanoj plazmi.Dobijeni rezultati mogu biti korisni kao osnova za razvoj i razumevanje novih antitumorski aktivnih kompleksa, kao i za razumevanje interakcija između kompleksa prelaznih metala i molekula od biološkog značaja.The subject of this dissertation was biospeciation of Y(III) ion in human blood plasma. To this end characterization of complexation equilibria of Y3+ with DTPA, DOTA and ciprofloxacine and production of yttrium-90 from Sr/Y generator was made.Hydrolysis and complexation of yttrium were investigated using potentiometricmesurenment with glass electrode in 0.15 mol dm-3 NaCl ionic medium, at 310.0 ± 0.5 К. In addition, data of the hydrolysis of yttrium (III) ion and complexation of yttrium (III) ion with DTPA and DOTA were obtained by ESI MS technique. Morphologies of various kinds of yttrium-hydroxide precipitates were examined using a scanning electron microscopy. Precipitates were also analyzed by thermogravimetric analysis (TGA) and infrared spectroscopy using KBr pill technique. Computer modeling May model was used for the determination of yttrium species in human plasma and certain dominant yttrium complexes with small molecules. The second part of the Thesis relate to the separation of90Y from 90Sr with high radiochemical yield and purity, that can be used for labelling organic molecules (DTPA and DOTA) which are used in nuclear medicine.The obtained results can be sumarized as follows: The stability constants of hydrolitic complexes (log β,.q) were: Y(OH)2+ (log β1,-1 = -7.71 ± 0.05), Y(OH)2+ (log β1,-2 = -16.42 ± 0.03), Y(OH)3 (log β1,-3 = -26.01± 0.03),Y2(OH)2 4+(log β2,-2 = -14.23± 0.05), Y3(OH)54+ (log β3,-5 = -34.20 ± 0.07) иY4(OH)66+(log β4,-6 = -37.10 ± 0.08). Hydrolytic species determined by potentiometric method were confirmed by ESIMS method also. Hydrolytic species containing tetramer ions with high charges were: [Y4(OH)4(H2O)2]8+, [Y4(OH)2Cl2]8+ и [Y4(OH)3ClH2O]8+. The hydrolytic precipitation reactions with NaOH or urea as precipitating agents were studied. The obtained precipitates were characterized by the X-ray diffraction, the SEM technique, thermal analysis (TG-DSC) and infrared spectroscopy. Powder X-ray diffraction (XRD) characterization indicated that the product, which was obtained by a hydrothermal method, could be indexed to a pure hexagonal phase of Y(OH)3, [space group: P63/m], and no peak shifts and other impurity phases appear. Scanning electron microscopy (SEM) observations indicated that the product was composed of chaotic spread needle particles. These needles were relatively uniform in size length of 8 μm and up to half a micron thick. The thermogravimetric and infrared analysis of the precipitate indicated a adsorbed and crystal water which were lost at higher temperatures. Transformation of the yttrium- hydroxide in yttrium-oxide was made at 873 K. Stability constants of protonated DTPA (log βp.q) were determined bypotentiometric method: HDTPA (logβ1,1 = 9.95±0.02), H2DTPA (logβ1,2 =18.68±0.01), H3DTPA (logβ1,3 = 23.30±0.03), H4DTPA (logβ1,4 = 26.55±0.02) иH5DTPA (logβ1,5 = 29.51±0.03). Investigation of complexation in the system Y(III)-DTPA indicated that protonated and non-protonated complexes exist in solution with stability constants (log βp.q,r):[YDTPA]2-(logβ1,1,0 = 22.51±0.03) и [YHDTPA]-(logβ1,1,1 = 24.41±0.05). The speciation of Y(III)-ions in human plasma has been studied by computersimulation using the program HySS2006. May’s model that included 43 ligands (26 amino acids, 7 inorganic ligands, 8 carboxylic acids, 2 protein) and 9 metal ions which are dominant in human blood plasma (Ca2+, Mg2+, Zn2+, Pb2+, Mn2+, Fe2+,Fe3+, Zn 2+ and Cu2+) was used. Stability constants of metal ions with ligads were taken from literature. Concentration of yttrium in the model was 1 × 10-9 mol dm-3, which corresponds to the concentration that is used in radionuclide therapy. In normal serum Y(III) ion is bound to citrates (YCit = 47.63 % and YCit2 = 2.98 %)and carbonates (Y(CO3)2 = 32.46 % and Y(CO3) = 10.60 %). Amount ofyttrium bound to oxalate is very small (YOxa = 1.57 %). Increasing the totalconcentrations of yttrium up to 1× 10–8 mol dm–3and 1× 10–7 mol dm–3 complexes of yttrium with citrates are still dominant species with unchanged share of 85.64% and 98.98%. Further increasing concentrations of Y(III) ions from 1× 10–6 mol dm-3 up to 1× 10-3 mol dm-3, leads to appearance of insoluble species of yttriumcarbonates Y2(CO3)3(s)). Separation of yttrium(III) from strontium(II) with 15 % (v/v) di(2-ethylhexyl) phosphoric acid (DEHPA) in dodecane was carried out in a hollow fiber supported liquid membrane (SLM) extraction system operated under closed-loop recirculation of the donor and acceptor phase. The effect of different flow rate of donor and acceptor in the extraction of Sr(II) and Y(III) ions were investigated. Optimal conditions were found (QA = 0.8 cm3 min -1and QD = 4.7 cm3 min-1) when the yield of Y(III) in the acceptor phase reached 60 % after 360 min with a molar ratio of Y(III) to Sr(II) in the acceptor of 250:1, as compared to1:25 in the donor phase. Preparation of 90Y in ,,home-made" 90Sr/90Y generators with defined chemical and radiochemical purity was carried out electrochemicaly in two cycle electrolysis procedure. Quality control of the resulting yttrium is determined by "BARC" technique and subsequently used for labelling DOTATATE. Control of the labeledproduct was performed by HPLC using SepPak C-18 columns

Biospecijacija itrijum(III)-jona i njegovih radiofarmaceutika

Radiofarmaceutici bazirani na različitim molekulima obeleženimitrijumom-90, se koriste pri tretmanu neoperativnih vrsta tumora, kao i u radijacionoj sinovektomiji. Veliko interesovanje za korišćenje 90Y u terapeutske svrhe potiče zbog njegovih nuklearnih karakteristika (t1/2=64,1, Eβ,max= 2,3 MeV,bez emisije zračenja). Dostupnost 90Y sa vrlo niskom radiohemijskom kontaminacijom je od suštinske važnosti u terapeutskoj primeni.Postojanje dugoživućeg pretka 90Sr sa vremenom poluživota od 28,9 godina i kratkoživućeg potomka 90Y nam omogućavaju formiranje generatorskog sistema. Iako postoje nekoliko vrsta generatora, prema literaturnim podacima, elektrohemijski generatori i generatori zasnovani na tečnim membranama imaju najveću perspektivu.Membranska ekstrakcija se takođe naziva i pertrakcija i bazirana je natrofaznom sistemu sa organskom fazom (tečna membrana) koja se nalazi između dve vodene faze i predstavlja alternativnu metodu klasičnoj tečno-tečnoj ekstrakciji. Prema literaturnim podacima, koristi se za razdvajanje širokog opsega rastvorenih supstanci uključujući biološke molekule, metalne jone, organske zagađivače i radionuklide.Elektrohemijska metoda je predložena kao rešenje pri separaciji 86Y od 86Sr i dobijanje 86Y koji služi pri pozitronsko emisionoj tomografiji (PET).Literaturni podaci pokazuju da elektrohemijska separacija predstavlja dobro rešenje jer omogućava veliku efikasnost uz minimalnu kontaminaciju okolnog prostora.Radiofarmaceutici koji se koriste u terapiji su u hemijskom smislukompleksna jedinjenja u kojima se kao centralni joni javljaju radioaktivni izotopi metala sa ili raspadom, dok su ligandi organski molekuli koji su sposobni da stvaraju helate. Ovi molekuli pored toga što su helatori za radiometal imaju i ulogu da se vežu za biomolekul. Zbog toga se i nazivaju bifunkcionalni helatori. Najpoznatiji i do sada najviše korišćeni bifunkcionalni helatori u radiohemiji itrijuma su: 1,4,7,10-tetraazociklododekan-1,4,7,10-tetraacetatna kiselina (DOTA) i dietilentriamin-pentasirćetna kiselina (DTPA).Klinička ispitivanja pokazuju da je eliminacija radiofarmaceutika izorganizma uglavnom brza i potpuna. Smatra se i da je metabolička transformacija radiofarmaceutika uglavnom minimalna. Međutim, u određenim uslovima može doći do ispoljavanja toksičnih efekata itrijuma i to kada je eliminacija radiofarmaceutika sprečena ili produžena i kada dolazi do disocijacije radiofarmaceutika. Tada se itrijum raspodeljuje između različitih liganada krvne plazme, prvenstveno, fosfata, karbonata i hidroksida. Biospecijacijazavisi ne samo od prirode radiofarmaceutika već i od prisustva drugihpotencijalnih liganada u krvnoj plazmi kao i neorganskih jona. Premaliteraturnim podacima specijacija i biodistribucija Y(III)-jona u humanoj plazmi, su proučavane u prisustvu ograničenog broja liganada, tako da postoji potreba da se proširi broj liganada koji se koristi prilikom ispitivanja. Tako je, pored već navedenih bifunkcionalnih helatora, u istraživanje uključen i ciprofloksacin, koji predstavlja četvrtu generaciju hinolona aktivnih na Gram-pozitivne bakterije i atipične patogene koji su uzročnici infekcija respiratornog trakta. Kako se Y(III)-jon u organizam unosi kompleksiran ligandima DTPA i DOTA koji se koriste u nuklearnoj medicini potrebno je i njih uključiti prilikom proračuna raspodele ovog jona u humanoj plazmi.Smatra se da je Y(III)-jon u organizmu uglavnom prisutan u obliku svojih hidrolitičkih kompleksa. Odavde može da se zaključi da interakcija Y(III)-jona i liganada u biološkim uslovima predstavlja interakcije sa hidrolitičkim kompleksima itrijuma.U prethodnih trideset godina, hidroliza itrijuma je proučavana povremeno pomoću različitih metoda ali nikada nije sistematski istraženo forimiranje hidrolitičkim kompleksa itrijuma. U literaturi mogu da se nađu pojedinačna ispitivanja hidrolize itrijuma ili termogravimetrijska analiza taloga itrijum-hidroksida, ali ne i podaci o ispitivanju na masenom spektrometru.Potenciometrijske metode daju najkorisnije informacije o vrstamahidrolitičkih komleksa, kao i o njihovim konstantama stabilnosti. Masena spektrometrija nam takođe može dati dosta podataka o vrstama hidrolitičkih kompleksa koje mogu da se jave u rastvorima.Stabilnost komleksa itrijuma sa DTPA, DOTA i ciprofloksacinom se možeodređivati potenciometrijski i masenospektrometrijskim merenjima.Cilj istraživanja ove doktorske teze predstavlja iznalaženje hidrolitičkih vrsta i određivanje njihovih konstati u sistemima koji su kompatibilni sa humanom krvnom plazmom (vodeni rastovor 0,15 mol dm-3 NaCl na 310,0 K). Takođe određivanje konstanti stabilnosti itrijuma sa DTPA i ciprofloksacinom omogućava dobijanje podataka koji se koriste pri specijaciji i određivanju biodistribucije Y(III)-jona u humanoj plazmi.Dobijeni rezultati mogu biti korisni kao osnova za razvoj i razumevanje novih antitumorski aktivnih kompleksa, kao i za razumevanje interakcija između kompleksa prelaznih metala i molekula od biološkog značaja.The subject of this dissertation was biospeciation of Y(III) ion in human blood plasma. To this end characterization of complexation equilibria of Y3+ with DTPA, DOTA and ciprofloxacine and production of yttrium-90 from Sr/Y generator was made.Hydrolysis and complexation of yttrium were investigated using potentiometricmesurenment with glass electrode in 0.15 mol dm-3 NaCl ionic medium, at 310.0 ± 0.5 К. In addition, data of the hydrolysis of yttrium (III) ion and complexation of yttrium (III) ion with DTPA and DOTA were obtained by ESI MS technique. Morphologies of various kinds of yttrium-hydroxide precipitates were examined using a scanning electron microscopy. Precipitates were also analyzed by thermogravimetric analysis (TGA) and infrared spectroscopy using KBr pill technique. Computer modeling May model was used for the determination of yttrium species in human plasma and certain dominant yttrium complexes with small molecules. The second part of the Thesis relate to the separation of90Y from 90Sr with high radiochemical yield and purity, that can be used for labelling organic molecules (DTPA and DOTA) which are used in nuclear medicine.The obtained results can be sumarized as follows: The stability constants of hydrolitic complexes (log β,.q) were: Y(OH)2+ (log β1,-1 = -7.71 ± 0.05), Y(OH)2+ (log β1,-2 = -16.42 ± 0.03), Y(OH)3 (log β1,-3 = -26.01± 0.03),Y2(OH)2 4+(log β2,-2 = -14.23± 0.05), Y3(OH)54+ (log β3,-5 = -34.20 ± 0.07) иY4(OH)66+(log β4,-6 = -37.10 ± 0.08). Hydrolytic species determined by potentiometric method were confirmed by ESIMS method also. Hydrolytic species containing tetramer ions with high charges were: [Y4(OH)4(H2O)2]8+, [Y4(OH)2Cl2]8+ и [Y4(OH)3ClH2O]8+. The hydrolytic precipitation reactions with NaOH or urea as precipitating agents were studied. The obtained precipitates were characterized by the X-ray diffraction, the SEM technique, thermal analysis (TG-DSC) and infrared spectroscopy. Powder X-ray diffraction (XRD) characterization indicated that the product, which was obtained by a hydrothermal method, could be indexed to a pure hexagonal phase of Y(OH)3, [space group: P63/m], and no peak shifts and other impurity phases appear. Scanning electron microscopy (SEM) observations indicated that the product was composed of chaotic spread needle particles. These needles were relatively uniform in size length of 8 μm and up to half a micron thick. The thermogravimetric and infrared analysis of the precipitate indicated a adsorbed and crystal water which were lost at higher temperatures. Transformation of the yttrium- hydroxide in yttrium-oxide was made at 873 K. Stability constants of protonated DTPA (log βp.q) were determined bypotentiometric method: HDTPA (logβ1,1 = 9.95±0.02), H2DTPA (logβ1,2 =18.68±0.01), H3DTPA (logβ1,3 = 23.30±0.03), H4DTPA (logβ1,4 = 26.55±0.02) иH5DTPA (logβ1,5 = 29.51±0.03). Investigation of complexation in the system Y(III)-DTPA indicated that protonated and non-protonated complexes exist in solution with stability constants (log βp.q,r):[YDTPA]2-(logβ1,1,0 = 22.51±0.03) и [YHDTPA]-(logβ1,1,1 = 24.41±0.05). The speciation of Y(III)-ions in human plasma has been studied by computersimulation using the program HySS2006. May’s model that included 43 ligands (26 amino acids, 7 inorganic ligands, 8 carboxylic acids, 2 protein) and 9 metal ions which are dominant in human blood plasma (Ca2+, Mg2+, Zn2+, Pb2+, Mn2+, Fe2+,Fe3+, Zn 2+ and Cu2+) was used. Stability constants of metal ions with ligads were taken from literature. Concentration of yttrium in the model was 1 × 10-9 mol dm-3, which corresponds to the concentration that is used in radionuclide therapy. In normal serum Y(III) ion is bound to citrates (YCit = 47.63 % and YCit2 = 2.98 %)and carbonates (Y(CO3)2 = 32.46 % and Y(CO3) = 10.60 %). Amount ofyttrium bound to oxalate is very small (YOxa = 1.57 %). Increasing the totalconcentrations of yttrium up to 1× 10–8 mol dm–3and 1× 10–7 mol dm–3 complexes of yttrium with citrates are still dominant species with unchanged share of 85.64% and 98.98%. Further increasing concentrations of Y(III) ions from 1× 10–6 mol dm-3 up to 1× 10-3 mol dm-3, leads to appearance of insoluble species of yttriumcarbonates Y2(CO3)3(s)). Separation of yttrium(III) from strontium(II) with 15 % (v/v) di(2-ethylhexyl) phosphoric acid (DEHPA) in dodecane was carried out in a hollow fiber supported liquid membrane (SLM) extraction system operated under closed-loop recirculation of the donor and acceptor phase. The effect of different flow rate of donor and acceptor in the extraction of Sr(II) and Y(III) ions were investigated. Optimal conditions were found (QA = 0.8 cm3 min -1and QD = 4.7 cm3 min-1) when the yield of Y(III) in the acceptor phase reached 60 % after 360 min with a molar ratio of Y(III) to Sr(II) in the acceptor of 250:1, as compared to1:25 in the donor phase. Preparation of 90Y in ,,home-made" 90Sr/90Y generators with defined chemical and radiochemical purity was carried out electrochemicaly in two cycle electrolysis procedure. Quality control of the resulting yttrium is determined by "BARC" technique and subsequently used for labelling DOTATATE. Control of the labeledproduct was performed by HPLC using SepPak C-18 columns

Biospecijacija itrijum(III)-jona i njegovih radiofarmaceutika

Radiofarmaceutici bazirani na različitim molekulima obeleženim itrijumom-90, se koriste pri tretmanu neoperativnih vrsta tumora, kao i u radijacionoj sinovektomiji. Veliko interesovanje za korišćenje 90Y u terapeutske svrhe potiče zbog njegovih nuklearnih karakteristika (t1/2=64,1, Eβ,max= 2,3 MeV,bez emisije zračenja). Dostupnost 90Y sa vrlo niskom radiohemijskom kontaminacijom je od suštinske važnosti u terapeutskoj primeni. Postojanje dugoživućeg pretka 90Sr sa vremenom poluživota od 28,9 godina i kratkoživućeg potomka 90Y nam omogućavaju formiranje generatorskog sistema. Iako postoje nekoliko vrsta generatora, prema literaturnim podacima, elektrohemijski generatori i generatori zasnovani na tečnim membranama imaju najveću perspektivu. Membranska ekstrakcija se takođe naziva i pertrakcija i bazirana je na trofaznom sistemu sa organskom fazom (tečna membrana) koja se nalazi između dve vodene faze i predstavlja alternativnu metodu klasičnoj tečno-tečnoj ekstrakciji. Prema literaturnim podacima, koristi se za razdvajanje širokog opsega rastvorenih supstanci uključujući biološke molekule, metalne jone, organske zagađivače i radionuklide. Elektrohemijska metoda je predložena kao rešenje pri separaciji 86Y od 86Sr i dobijanje 86Y koji služi pri pozitronsko emisionoj tomografiji (PET). Literaturni podaci pokazuju da elektrohemijska separacija predstavlja dobro rešenje jer omogućava veliku efikasnost uz minimalnu kontaminaciju okolnog prostora. Radiofarmaceutici koji se koriste u terapiji su u hemijskom smislu kompleksna jedinjenja u kojima se kao centralni joni javljaju radioaktivni izotopi metala sa ili raspadom, dok su ligandi organski molekuli koji su sposobni da stvaraju helate. Ovi molekuli pored toga što su helatori za radiometal imaju i ulogu da se vežu za biomolekul. Zbog toga se i nazivaju bifunkcionalni helatori. Najpoznatiji i do sada najviše korišćeni bifunkcionalni helatori u radiohemiji itrijuma su: 1,4,7,10-tetraazociklododekan-1,4,7,10-tetraacetatna kiselina (DOTA) i dietilentriamin-pentasirćetna kiselina (DTPA). Klinička ispitivanja pokazuju da je eliminacija radiofarmaceutika iz organizma uglavnom brza i potpuna. Smatra se i da je metabolička transformacija radiofarmaceutika uglavnom minimalna. Međutim, u određenim uslovima može doći do ispoljavanja toksičnih efekata itrijuma i to kada je eliminacija radiofarmaceutika sprečena ili produžena i kada dolazi do disocijacije radiofarmaceutika. Tada se itrijum raspodeljuje između različitih liganada krvne plazme, prvenstveno, fosfata, karbonata i hidroksida. Biospecijacija zavisi ne samo od prirode radiofarmaceutika već i od prisustva drugih potencijalnih liganada u krvnoj plazmi kao i neorganskih jona. Prema literaturnim podacima specijacija i biodistribucija Y(III)-jona u humanoj plazmi, su proučavane u prisustvu ograničenog broja liganada, tako da postoji potreba da se proširi broj liganada koji se koristi prilikom ispitivanja. Tako je, pored već navedenih bifunkcionalnih helatora, u istraživanje uključen i ciprofloksacin, koji predstavlja četvrtu generaciju hinolona aktivnih na Gram-pozitivne bakterije i atipične patogene koji su uzročnici infekcija respiratornog trakta. Kako se Y(III)-jon u organizam unosi kompleksiran ligandima DTPA i DOTA koji se koriste u nuklearnoj medicini potrebno je i njih uključiti prilikom proračuna raspodele ovog jona u humanoj plazmi. Smatra se da je Y(III)-jon u organizmu uglavnom prisutan u obliku svojih hidrolitičkih kompleksa. Odavde može da se zaključi da interakcija Y(III)-jona i liganada u biološkim uslovima predstavlja interakcije sa hidrolitičkim kompleksima itrijuma. U prethodnih trideset godina, hidroliza itrijuma je proučavana povremeno pomoću različitih metoda ali nikada nije sistematski istraženo forimiranje hidrolitičkim kompleksa itrijuma. U literaturi mogu da se nađu pojedinačna ispitivanja hidrolize itrijuma ili termogravimetrijska analiza taloga itrijum-hidroksida, ali ne i podaci o ispitivanju na masenom spektrometru. Potenciometrijske metode daju najkorisnije informacije o vrstama hidrolitičkih komleksa, kao i o njihovim konstantama stabilnosti. Masena spektrometrija nam takođe može dati dosta podataka o vrstama hidrolitičkih kompleksa koje mogu da se jave u rastvorima. Stabilnost komleksa itrijuma sa DTPA, DOTA i ciprofloksacinom se može određivati potenciometrijski i masenospektrometrijskim merenjima. Cilj istraživanja ove doktorske teze predstavlja iznalaženje hidrolitičkih vrsta i određivanje njihovih konstati u sistemima koji su kompatibilni sa humanom krvnom plazmom (vodeni rastovor 0,15 mol dm-3 NaCl na 310,0 K). Takođe određivanje konstanti stabilnosti itrijuma sa DTPA i ciprofloksacinom omogućava dobijanje podataka koji se koriste pri specijaciji i određivanju biodistribucije Y(III)-jona u humanoj plazmi. Dobijeni rezultati mogu biti korisni kao osnova za razvoj i razumevanje novih antitumorski aktivnih kompleksa, kao i za razumevanje interakcija između kompleksa prelaznih metala i molekula od biološkog značaja.The subject of this dissertation was biospeciation of Y(III) ion in human blood plasma. To this end characterization of complexation equilibria of Y 3+ with DTPA, DOTA and ciprofloxacine and production of yttrium-90 from Sr/Y generator was made. Hydrolysis and complexation of yttrium were investigated using potentiometric mesurenment with glass electrode in 0.15 mol dm-3 NaCl ionic medium, at 310.0 ± 0.5 К. In addition, data of the hydrolysis of yttrium (III) ion and complexation of yttrium (III) ion with DTPA and DOTA were obtained by ESI MS technique. Morphologies of various kinds of yttrium-hydroxide precipitates were examined using a scanning electron microscopy. Precipitates were also analyzed by thermogravimetric analysis (TGA) and infrared spectroscopy using KBr pill technique. Computer modeling May model was used for the determination of yttrium species in human plasma and certain dominant yttrium complexes with small molecules. The second part of the Thesis relate to the separation of 90Y from 90Sr with high radiochemical yield and purity, that can be used for labelling organic molecules (DTPA and DOTA) which are used in nuclear medicine. The obtained results can be sumarized as follows: The stability constants of hydrolitic complexes (log β,.q) were: Y(OH)2+ (log β1,-1 = -7.71 ± 0.05), Y(OH)2 + (log β1,-2 = -16.42 ± 0.03), Y(OH)3 (log β1,-3 = -26.01± 0.03), Y2(OH)2 4+(log β2,-2 = -14.23± 0.05), Y3(OH)5 4+ (log β3,-5 = -34.20 ± 0.07) и Y4(OH)6 6+ (log β4,-6 = -37.10 ± 0.08). Hydrolytic species determined by potentiometric method were confirmed by ESIMS method also. Hydrolytic species containing tetramer ions with high charges were: [Y4(OH)4(H2O)2]8+, [Y4(OH)2Cl2] 8+ и [Y4(OH)3ClH2O]8+. The hydrolytic precipitation reactions with NaOH or urea as precipitating agents were studied. The obtained precipitates were characterized by the X-ray diffraction, the SEM technique, thermal analysis (TG-DSC) and infrared spectroscopy. Powder X-ray diffraction (XRD) characterization indicated that the product, which was obtained by a hydrothermal method, could be indexed to a pure hexagonal phase of Y(OH)3, [space group: P63/m], and no peak shifts and other impurity phases appear. Scanning electron microscopy (SEM) observations indicated that the product was composed of chaotic spread needle particles. These needles were relatively uniform in size length of 8 μm and up to half a micron thick. The thermogravimetric and infrared analysis of the precipitate indicated a adsorbed and crystal water which were lost at higher temperatures. Transformation of the yttrium- hydroxide in yttrium-oxide was made at 873 K. Stability constants of protonated DTPA (log βp.q) were determined by potentiometric method: HDTPA (logβ1,1 = 9.95±0.02), H2DTPA (logβ1,2 = 18.68±0.01), H3DTPA (logβ1,3 = 23.30±0.03), H4DTPA (logβ1,4 = 26.55±0.02) и H5DTPA (logβ1,5 = 29.51±0.03). Investigation of complexation in the system Y(III)-DTPA indicated that protonated and non-protonated complexes exist in solution with stability constants (log βp.q,r): [YDTPA]2-(logβ1,1,0 = 22.51±0.03) и [YHDTPA]-(logβ1,1,1 = 24.41±0.05). The speciation of Y(III)-ions in human plasma has been studied by computer simulation using the program HySS2006. May’s model that included 43 ligands (26 amino acids, 7 inorganic ligands, 8 carboxylic acids, 2 protein) and 9 metal ions which are dominant in human blood plasma (Ca2+, Mg2+, Zn2+, Pb2+, Mn2+, Fe2+,Fe3+, Zn 2+ and Cu2+) was used. Stability constants of metal ions with ligads were taken from literature. Concentration of yttrium in the model was 1 × 10-9 mol dm-3, which corresponds to the concentration that is used in radionuclide therapy. In normal serum Y(III) ion is bound to citrates (YCit = 47.63 % and YCit2 = 2.98 %) and carbonates (Y(CO3)2 = 32.46 % and Y(CO3) = 10.60 %). Amount of yttrium bound to oxalate is very small (YOxa = 1.57 %). Increasing the total concentrations of yttrium up to 1× 10–8 mol dm–3 and 1× 10–7 mol dm–3 complexes of yttrium with citrates are still dominant species with unchanged share of 85.64% and 98.98%. Further increasing concentrations of Y(III) ions from 1× 10–6 mol dm-3 up to 1× 10-3 mol dm-3 , leads to appearance of insoluble species of yttriumcarbonates Y2(CO3)3(s)). Separation of yttrium(III) from strontium(II) with 15 % (v/v) di(2-ethylhexyl) phosphoric acid (DEHPA) in dodecane was carried out in a hollow fiber supported liquid membrane (SLM) extraction system operated under closed-loop recirculation of the donor and acceptor phase. The effect of different flow rate of donor and acceptor in the extraction of Sr(II) and Y(III) ions were investigated. Optimal conditions were found (QA = 0.8 cm3 min -1 and QD = 4.7 cm3 min-1) when the yield of Y(III) in the acceptor phase reached 60 % after 360 min with a molar ratio of Y(III) to Sr(II) in the acceptor of 250:1, as compared to1:25 in the donor phase. Preparation of 90Y in ,,home-made" 90Sr/ 90Y generators with defined chemical and radiochemical purity was carried out electrochemicaly in two cycle electrolysis procedure. Quality control of the resulting yttrium is determined by "BARC" technique and subsequently used for labelling DOTATATE. Control of the labeledproduct was performed by HPLC using SepPak C-18 columns

Numerical-experimental determination of stress and deformation state in connection lugs

The present paper describes the numerical and experimental methodology for the analysis of stress and deformation state in structural elements with geometrical discontinuities. Research is based on structural elements of the connection lug type and stress and deformation state. Numerical analysis is conducted by applying the finite ware package. Experiments are performed at the Laboratory for Stress and Deformation Measurements, Faculty of Mechanical Engineering, Belgrade, using GOM equipment the framework of the paper

Numerical-experimental determination of stress and deformation state in connection lugs

The present paper describes the numerical and experimental methodology for the analysis of stress and deformation state in structural elements with geometrical discontinuities. Research is based on structural elements of the connection lug type and stress and deformation state. Numerical analysis is conducted by applying the finite ware package. Experiments are performed at the Laboratory for Stress and Deformation Measurements, Faculty of Mechanical Engineering, Belgrade, using GOM equipment the framework of the paper

Optimizing a radiochemical separation of 26Al from an acidic V-rich matrix

Sorption and desorption of Al(III) on a series of different extraction resins (LN, LN2, LN3, TK100, TK101, TK201) in acidic HNO3 media containing high concentrations of V(IV,V) was investigated. Static batch studies were conducted as a way of obtaining preliminary distribution coefficient (Kd) values that were further used to develop dynamic tests on real samples. It was shown that a complete separation and recovery of Al(III) from V(V) under acidic conditions (pH = 2) is possible by utilizing LN resin. Active “hot” dynamic studies with 26Al (≈10 Bq) as a radiotracer and real waste samples were conducted to further investigate and confirm the results of the inactive “cold” experiments. Utilizing this separation procedure, we have successfully removed all traces of 26Al (∼10−9 g) radiotracer from the bulk vanadium matrix

Radiographic devices grammat se and gammavolt SU 50 with source 75SE and radiation protection

Zatvoreni radioaktivni izvor 75Se se sve više koristi u radiografskim kontrolama kompaktnosti materijala. Njegova energija γ-zračenja odgovara za kontrolu npr. čeličnih materijala debljine 5–30 mm. Za korišćenje ovih izvora služi uređaj novije generacije Gammamat SE. Međutim za radiografska ispitivanja sa 75Se može se koristiti i uređaj Gammavolt SU 50 ili Gammavolt SU 100 koji su od strane proizvođača namenjeni za korišćenje izvora 192Ir. U ovom radu su prikazani rezultati dozimetrijskih merenja koja se odnose na radiografske uređaje Gammamat SE i Gammavolt SU 50 u koje je ugrađen radioaktivni izvor 75Se aktivnosti 3TBq. Prikazane su prednosti i mane svakog uređaja sa aspekta eksploatacije u svakodnevnom radu i sa aspekta zaštite od zračenja.The closed radioactive source 75Se is increasingly used in radiographic controls of material compactness. Its radiation energy is suitable for control of steel materials of 5–30mm thickness. The new generation device Gammamat SE serves for the use of these sources. However, for radiographic testing with 75Se Gammavolt SU 50 or Gammavolt SU 100 may be used, although, according to their manufacturer, they should serve for using 192Ir source. This paper presents the results of dosimetric measurements relating to radiographic devices Gammamat SE and Gammavolt SU 50, with 75Se radioactive source with 3TBq activity. Advantages and disadvantages of each device were given from the aspect of exploitation in daily work and from the aspect of radiation protection.23. Međunarodni kongres o procesnoj industriji - PROCESING ′10: 26. savetovanje sa međunarodnim učešćem ZAVARIVANJE 2010 : 26. savetovanje sa međunarodnim učešćem IBR 2010 zbornik radova; 2-4. jun, Tar