Associative nature of event participation dynamics: a network theory approach

The affiliation with various social groups can be a critical factor when it comes to quality of life of each individual, making such groups an essential element of every society. The group dynamics, longevity and effectiveness strongly depend on group's ability to attract new members and keep them engaged in group activities. It was shown that high heterogeneity of scientist's engagement in conference activities of the specific scientific community depends on the balance between the numbers of previous attendances and non-attendances and is directly related to scientist's association with that community. Here we show that the same holds for leisure groups of the Meetup website and further quantify individual members' association with the group. We examine how structure of personal social networks is evolving with the event attendance. Our results show that member's increasing engagement in the group activities is primarily associated with the strengthening of already existing ties and increase in the bonding social capital. We also show that Meetup social networks mostly grow trough big events, while small events contribute to the groups cohesiveness.Comment: 16 pages, 6 figs + Supporting information 7 pages, 8 fig

Activities of antioxidative enzymes during Chenopodium rubrum L. ontogenesis in vitro

For the short-day plant Chenopodium rubrum, a 14 h/10 h photoperiod is inductive for flowering, while continuous light (CL) is noninductive. Plants of one group were grown continuously under ail inductive photoperiod, while in the other group flowering induction was delayed by 17 days of CL in order to separate oil the time scale different developmental phases in plants of the same age. Regardless of the photoperiodic conditions the plants were exposed to, seed maturation occurred in 10 weeks. Activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) were determined in different phases of development (vegetative growth, flowering, seed development, and maturation). The activities of antioxidative enzymes depended on both the phase of development and the photoperiod. In plants grown continuously under an inductive photoperiod, high CAT and POD activities were detected at the time of flowering and decreased during seed development and maturation. In plants in which flowering induction was delayed by 17 days of CL, the activities of POD and SOD were lowest in the vegetative phase of development and attained maximum values in the phase of seed maturation. In both groups of plants, the highest CAT activity was measured at the time of flowering

Effect of gibberellic acid on total antioxidant activity during chenopodium rubrum l. Ontogenesis in vitro

Total antioxidant activity (TAA) represents the combined ability of diverse antioxidants present in a sample of plant material to scavenge free radicals. Chenopodium rubrum L. sel. 184 is a qualitatively short-day plant; as an early-flowering species, it is a suitable object for studying ontogenesis in vitro. We investigated the effect of GA3 (5 mg/l) on TAA during C rubrum ontogenesis under two different inductive photoperiodic regimes in vitro. Total antioxidant activity does not change in different phases of C. rubrum ontogenesis under the same photoperiodic treatment. Exposure to continuous irradiation caused an increase of TAA in both C. rubrum plants and collected matured seeds. Gibberellic acid stimulated stem elongation, but did not affect leaf development or the number of matured seeds per plant, regardless of photoperiodic treatment; it induced a decrease of TAA in C rubrum plants regardless of photoperiodic treatment or the phase of development, while it had no effect on TAA of matured seeds

Inconsistency of modernist architect position in the XXI century practice

Рад преиспитује позицију архитектонског модернизма као кодекса који обликује дисциплинарно знање, претпостављајући дијалектички образац који се одликује унутрашњом противречношћу. Модерна је означавала историјску прекретницу у погледу геометријских атрибута грађевине, створивши услове за искорак од репрезентативности класичног језика ка апстрактном јединству облика, простора и функције. Сам покрет је утврђивањем универзалних парадигми тежио ка превазилажењу дивергентних услова архитектонске активности, формализујући њене процесе и дајући им систематски карактер као основ за конституисање аутономне дисциплине. Модернизам је представљао епистемолошко градилиште на коме је подигнут читав нови поредак праксе чији су конструкти, посредством историјских наратива, наткрилили тоталитет струковног искуства.The paper examines the position of architectural Modernism as the codex that shapes disciplinary knowledge, assuming a dialectical pattern characterized by internal contradiction. Modernism represented a historical milestone in terms of geometrical attributes of a building, achieving a decisive leap from the representability of the classical language to the abstract unity of form, space and function. By establishing universal paradigms, the movement itself sought to overcome the divergent conditions of architectural activity, formalizing its processes and giving them a systematic character as the basis for constituting of an autonomous discipline. Modernism was the epistemological construction site where the entire new order of practice was built, whose constructs, through historical narratives, surpassed the totality of professional experience..

Synthesis of conductive electroceramic material based on antimony doped barium stannate with linear current-voltage characteristic

U okviru ove disertacije ispitivani su uticaji koncentracije dopanta i parametara sinterovanja nastrukturu i svojstva keramičkih uzoraka barijum-stanata dopiranog antimonom, BaSn1-xSbxO3(BSSO, x = 0,00; 0,04; 0,06; 0,08 i 0,10) u cilju dobijanja provodne elektrokeramike sa linearnomstrujno-naponskom (I-U) karakteristikom...The main goal of this doctoral thesis was to investigate the influence of different dopantconcentrations and sintering parameters on the structure and properties of antimony-doped bariumstannate, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 and 0,10) to obtain conductiveelectroceramic samples with linear current-voltage (I-U) characteristics..

Dobijanje provodne elektrokeramike na bazi barijum-stanata dopiranog antimonom sa linearnom strujno-naponskom karakteristikom

U okviru ove disertacije ispitivani su uticaji koncentracije dopanta i parametara sinterovanja na strukturu i svojstva keramičkih uzoraka barijum-stanata dopiranog antimonom, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 i 0,10) u cilju dobijanja provodne elektrokeramike sa linearnom strujno-naponskom (I-U) karakteristikom. Smeša prahova BaCO3, SnO2 i Sb2O3 mehanički je aktivirana u izopropanolu, kalcinisana na 900 °C i potom sinterovana koristeći tri različite metode: konvencionalno, spark plazma i hladno sinterovanje. Konvencionalno sinterovanje prahova vršeno je na 1200, 1400 i 1600 °C, ali se na nižim temperaturama dobija keramički materijal niskih relativnih gustina. Sinterovanjem na 1600 °C dobijeni su jednofazni uzorci kubne strukture BaSnO3 (BSO). Rezultati skenirajuće elektronske mikroskopije (engl. Scanning Electron Microscopy, SEM) ukazuju na značajno smanjenje veličine zrna nakon dopiranja, ali i na poroznost koja ometa električnu karakterizaciju uzoraka. Transmisiona elektronska mikroskopija visoke rezolucije (engl. High Resolution Transmission Electron Microscopy, HRTEM) ukazuje na prisustvo niskougaonih granica zrna u uzorku BaSn0,92Sb0,08O3. Pouzdana električna merenja izvršena na ovom uzorku ukazuju na njegova poluprovodnička svojstva karakteristična za materijale sa dvostrukom Šotkijevom barijerom (engl. Schottky barrier) na granici zrna. Spark plazma sinterovanje (SPS) vršeno je na temperaturama od 1000, 1100, 1200 i 1250 °C, za vreme od 5, 10, 15 i 30 min, pri pritisku od 60 MPa i sa brzinom zagrevanja od 100 °C min–1. Za dobijanje guste keramike optimalni uslovi sinterovanja su 1100 i 1200 °C, tokom 5 min. Sinterovanjem na 1100 °C dobijeni su jednofazni keramički uzorci kubne strukture BSO. Dopiranje antimonom dovodi do smanjenja veličine zrna, ali i do smanjenja specifične otpornosti u odnosu na nedopirani uzorak. Električna karakterizacija ukazuje na poluprovodnička svojstva svih keramičkih uzoraka, sa najnižom specifičnom otpornošću zabeleženom na uzorku BaSn0,92Sb0,08O3. SPS na 1200 °C dobijaju se keramički uzorci koji osim kubne faze BSO, sadrže i sekundarnu fazu Ba2SnO4, čija se količina u uzorku smanjuje dopiranjem. Na ovoj temperaturi pri visokom pritisku dolazi do reakcije SnO2 iz kalcinisanog praha sa grafitom iz kalupa pri čemu se izdvaja elementarni kalaj i stvaraju uslovi za formiranje sekundarne faze bogate barijumom. Rezultati skenirajuće elektronske mikroskopije emisijom elektrona poljem (engl. Field Emission Scanning Electron Microscopy, FE-SEM) ovih uzoraka potvrđuju da dopiranjem dolazi do smanjenja veličine zrna, ali i smanjenja koncentracije iv dislokacija u keramičkim uzorcima. Svi uzorci osim BaSn0,92Sb0,08O3 ispoljavaju nelinearnu strujno-naponsku karakteristiku, tipičnu za poluprovodnike sa potencijalnom barijerom na granici zrna. Veliki udeo niskougaonih granica u uzorku BaSn0,92Sb0,08O3 dovodi do gubitka potencijalne barijere na granici zrna, što je potvrđeno i impedansnom spektroskopijom, pa ovaj uzorak pokazuje najnižu vrednost specifične otpornosti, konstantnu u temperaturnom opsegu 25–150 °C i linearnu strujno-naponsku karakteristiku. Za razliku od prethodne metode, hladno sinterovanje uzorka BaSn0,92Sb0,08O3 nije dalo zadovoljavajuće rezultate po pitanju faznog sastava, gustine i električnih svojstava. Redukcioni uslovi tipični za spark plazma sinterovanje, uz koncentraciju dopanta od 8 % (mol.) Sb u uzorku BaSnO3 doveli su do formiranja niskougaonih granica zrna, povećanja koncentracije vakancija kiseonika i promene valence Sn, što je dovelo do porasta koncentracije nosilaca naelektrisanja (elektrona) i posledično rezultovalo dobijanjem uzorka sa linearnom I-U karakteristikom i konstantnom vrednosti specifične otpornosti u širem temperaturnom opsegu.The main goal of this doctoral thesis was to investigate the influence of different dopant concentrations and sintering parameters on the structure and properties of antimony-doped barium stannate, BaSn1-xSbxO3 (BSSO, x = 0,00; 0,04; 0,06; 0,08 and 0,10) to obtain conductive electroceramic samples with linear current-voltage (I-U) characteristics. A mixture of BaCO3, SnO2 and Sb2O3 powders was mechanically activated in isopropanol, calcined at 900 °C and then sintered using three different methods: conventional, spark plasma and cold sintering. Conventional sintering at 1200 and 1400 °C resulted in the preparation of low-density ceramic samples. By sintering at 1600 °C, single-phase material with a cubic BaSnO3 (BSO) structure was obtained. The scanning electron microscopy results (SEM) indicate a significant decrease in grain size upon doping but also reveal porosity, which hinders the electrical characterization of the samples. High resolution transmission electron microscopy (HRTEM) indicates the presence of low-angle grain boundaries (LAGBs) in the BaSn0.92Sb0.08O3 sample. Reliable electrical measurements performed on this sample indicate its semiconducting properties characteristic of materials with a double Schottky barrier at the grain boundary. Spark plasma sintering (SPS) was performed at temperatures 1000, 1100, 1200 and 1250 °C, for 5, 10, 15 and 30 min, at a pressure of 60 MPa and with a heating rate of 100 °C min–1. The most optimal conditions for the preparation of dense ceramic materials, in terms of temperatures and sintering time, were 1100 and 1200 °C for 5 min. By sintering at 1100 °C, single-phase ceramic samples with a cubic BSO structure were obtained. In comparison to the undoped sample, doping with Sb leads to a decrease in both grain size and electrical resisitivity. Electrical characterization shows semiconducting properties of all ceramic materials, with the lowest resistivity recorded for the BaSn0.92Sb0.08O3 sample. Apart from the cubic BSO, the spark plasma sintered samples at 1200 °C contained Ba2SnO4 as a secondary phase, whose content decreases upon doping. High sintering temperature and applied pressure created conditions for the reaction of SnO2 from the calcined powder with graphite from the mould, resulting in the evaporation of metallic tin and the formation of the barium-rich secondary phase. The field emission scanning electron microscopy (FE-SEM) results confirm that doping leads to a decrease in grain size and the concentration of dislocations in these ceramic samples. All samples except BaSn0.92Sb0.08O3 exhibit nonlinear current-voltage characteristics, typical for semiconductors with a vi potential barrier at the grain boundary. As a consequence of higher amount of LAGBs present in it, the ceramic BaSn0.92Sb0.08O3, showed linear I-U characteristics in the whole temperature measurement range (25–150 °C) and a significant drop in the electrical resistivity due to the loss of potential barrier at grain boundary. The impedance spectroscopy confirmed these assumptions. Unlike the previous method, cold sintering of the BaSn0.92Sb0.08O3 sample did not give satisfactory results either in phase composition and density or electrical properties. The reducing conditions typical for spark plasma sintering and the dopant concentration of 8 % (mol) Sb in the BaSnO3 sample led to the formation of LAGBs, an increase in the concentration of oxygen vacancies and a change in the valence state of Sn, consequently leading to increase in the charge carriers (electrons) concentration and resulting in the ceramic sample with a linear I-U characteristic and a constant value of electric resistivity in a wide temperature range

PASSENGER CAR USAGE FOR COMMUTING TO WORK AS A FUNCTION OF LIMITED STAY AT CAR PARKS

The analysis of the experiences in European cities, following the implementation of different transport policy measures, has led to a conclusion that parking policy measures have the dominant effect on the choice of private car as a mode of transport. This effect is the greatest for the commutes to work, characterized by the longest duration of parking space occupancy. Given the aforementioned experiences in developed European cities, the main aim of the study presented here was the determination of a relationship between limiting the duration of parking space occupancy in the Novi Sad city centre and the transport participants’ decision whether or not to use passenger car to commute to work. Based on the established interdependence between these parameters, we developed a mathematical model for calculating a number of expected car (commuting) journeys that terminate in the city centre as a function of limited duration of parking space occupancy.  </p

Food tourism concept - creating synergy between urban and rural places - case study of Maglič, Serbia

Food tourism is being seen as one of the fastest growing industries over the second half of the twentieth century (e.g. Saeter, 1998; Smith, 1988) and a key support for the rural development. In declining rural areas, food tourism is often seen as an additional economic activity and a method of retaining rural regions (Font and Ahjem, 1999). Urban-rural connections are important for poverty assuagement, sustainable rural land use and balanced territorial development in general. Additionally, strong bonds can improve the overall living conditions and employment chances for both rural and urban areas (Tacoli, 1998, 2003; Rosenthal, 2000). The primary purpose of this study is to foster relationships between urban and rural areas by developing a concept proposal for food tourism, through the........ at the Faculty of Architecture, University of Belgrade. The proposal was created during the two theoretical and project-based courses, focused on the sustainable planning and design in the natural environment. The location chosen for the project is a medieval fortress ..... with its surroundings, located in the gorge of Ibar, 20 km south of the city of Kraljevo. Having lost its primary function, the site is nowadays poorly visited. This problem is seen as a challenge to reinvent the urban/rural landscape and create an attractive ambient which relates to the revitalised historical site. As a result, the specific concept of food tourism called “slow food” is developed, both based on tradition and modern values, further elaborated through the planning proposal and urban design project. Following the specific planning and urban design methodology, the extensive research is drawn upon mostly primary and secondary sources, including analysis of urban plans in different scales, comprehensive literature review, as well as cooperation with local authorities and institutions. The full purpose and value of the proposal are confirmed by the city government of Kraljevo and several city agencies and institutes, as the proposal initialized the discussion and revival of the ideas for the important but forgotten historic place and its rural background

Electronic lexical resources and tools for natural language processing of Serbian and their improvement via crowdsourcing

Овај докторски рад бави се истраживањем најбољег начина да се унапреде језички ресурси и алати за обраду српског језика, са нагласком на обради фигуративног језика, то јест језика који је богат реторичким фигурама. У раду су представљени језички ресурси и алати за обраду српског језика, нарочито Ворднет и Српски ворднет, чија доградња је централни део овог истраживања. Та доградња је спроведена путем модела такозване групне расподеле рада, како смо за потребе израде овог рада превели енглески термин crowdsourcing...The research presented in this doctoral thesis deals with finding the best way to enhance lexical resources and tools for natural language processing of Serbian language, with a focus on processing of figurative language, i.e. language in which plenty of rhetorical figures are used. The thesis presents lexical resources and tools for natural language processing of Serbian language, especially WordNet and Serbian wordnet, whose enhancment and building via the crowdsourcing model are the central part of the presented research results..

Molecular chaperonin large subunit gene (gro EL gene) as an additional marker for differntiation of 'Canidatus Phytoplasma asteris' - related strains

Na teritoriji Republike Srbije su u periodu od 2009. do 2011. godine sakupljeni uzorci biljaka sa simptomima karakterističnim za prisustvo fitoplazmi. Upotrebom PCR metode pomoću univerzalnih prajmera P1/P7 i R16F2n/R16R2 u njima su detektovane fitoplazme. Upotrebom restrikcionih enzima Tru1I, HhaI, RsaI i Tsp509I na R16F2n/R16R2 amplikone, ove fitoplazme su na osnovu dobijenih restrikcionih profila identifikovane kao Aster yellows fitoplazme (ribozomalna grupa 16SrI), podgrupe 16SrI-B, I-C i I-P, odnosno kao Stolbur fitoplazme (ribozomalna grupa 16SrXII). Upotrebom iste PCR-RFLP metode kod 19 sojeva Aster yellows fitoplazmi iz kolekcije i tri soja poreklom iz šargarepe iz Srbije, potvrĎena je pripadnost podgrupama 16SrI-A, I-B, I-C i I-F preuzeta iz literature. TakoĎe je utvrĎena pripadnost odreĎenoj podgrupi kod četiri soja iz kolekcije, koji se prvi put koriste u analizi i o kojima nema literaturnih podataka. Upotrebom novodizajniranih prajmera AYgroesF/AYampR i AYgroelF/AYgroelR umnoţen je groEL gen kod sva 34 testirana soja Aster yellows fitoplazmi. Analizom restrikcionih profila dobijenih pomoću Tru1I i AluI restrikcionih enzima na AYgroelF/R amplikone, utvrĎeno je postojanje šest, odnosno osam različitih profila na osnovu kojih su svi testirani sojevi svrstani u devet groELI podgrupa (groELI-I do groELI-IX). Na osnovu groEL gena podgrupe 16SrI-A i I-C su dalje diferencirane u dve groELI podgrupe, 16SrI-B u tri, dok podgrupe 16SrI-M i I-L nisu pokazale nikakve meĎusobne razlike u odnosu na jedan deo podgrupe 16SrI-B. Podgrupe 16SrI-F i I-P se razlikuju od ostalih podgrupa i na nivou groEL gena kao i na nivou 16S rDNK. TakoĎe je utvrĎeno da sedam novodetektovanih sojeva Aster yellows fitoplazmi iz Srbije pripada podgrupama groELI-III, I-VII i I-IX. Analizom tuf gena, dela rp operona i secY gena kod 22 odabrana od 34 testirana soja soja Aster yellows fitoplazmi moguće je testirane sojeve klasifikovati u šest tufI i sedam rpI i secYI podgrupa na osnovu MboI, Tsp509I i Tru1I restrikcionih profila za tuf gen, HhaI, AluI i Tsp509I za rp gen i Tsp509I i Tru1I za secY gen. Podgrupa 16SrI-A je dalje diferencirana u dve tufI podgrupe, odnosno 16SrI-A i I-B u po dve rpI i secYI podgrupe, dok podgrupe 16SrI-B, I-M i I-L nisu pokazale nikakve meĎusobne razlike. Podgrupe 16SrI-C, I-F i I-P se razlikuju od ostalih podgrupa i na nivou sva tri testirana gena kao i na nivou 16S rDNKThe plant samples with symptoms typical for phytoplasma infection were collected in Serbia from 2009 till 2011. In those samples phytoplasmas were detected by PCR technique with universal primers P1/P7 and R16F2n/R16R2 and identified according to their Tru1I, HhaI, RsaI and Tsp509I restriction profiles of digested R16F2n/R16R2 amplicons as Aster yellows phytoplasma (ribosomal group 16SrI), subgroups 16SrI-B, I-C and I-P or as Stolbur phytoplasma (ribosomal group 16SrXII). Applying the same PCR-RFLP method on 19 strains of Aster yellows phytoplasmas from collection and three strains from carrot from Serbia, it was confirmed that this strains belong to subgroups 16SrI-A, I-B, I-C and I-F as stated in literature. Also the subgroups were determined for four strains from collection that are used in analyses for the first time and that have no literature data. Using newly designed primers AYgroesF/AYampR and AYgroelF/AYgroelR, the groEL gene was successfully amplified in all 34 strains of Aster yellows phytoplasma tested. RFLP analyses of AYgroelF/AYgroelR amplicons with Tru1I i AluI restriction enzymes revealed existence of six and eight different restriction profiles, respectively, according to which all tested strains were classified in nine groELI subgroups (groELI-I till groELI-IX). On the basis of groEL gene, subgroups 16SrI-A and I-C were further differentiated into two groELI subgroups, 16SrI-B into three, while subgroups 16SrI-M and I-L showed no difference to some strains belonging to subgroup 16SrI-B. Subgroups 16SrI-F and I-P could be differentiated from other subgroups on the basis of groEL gene as on the basis of 16S rDNA. The seven newly detected Aster yellows strains from Serbia were affiliated to subgroups groELI-III, I-VII and I-IX. RFLP analyses with MboI, Tsp509I and Tru1I restriction enzymes of tuf gene, HhaI, AluI and Tsp509I of rp gene and Tsp509I and Tru1I of secY gene, classified 22 selected Aster yellows strains into six tufI subgroups and seven rpI and secYI subgroups. Subgroup 16SrI-A was further differentiated into two tufI subgroups and subgroups 16SrI-A and I-B were further differentiated into two rpI and secYI subgroups each. On the other hand subgroups 16SrI-B, I-M and I-L showed no mutual differences, while subgroups 16SrI-C, I-F and I-P could be differentiated from other subgroups on the basis of all three genes tested as on the basis of 16S rDNA. RFLP analysis of tuf gen with HpaII restriction enzyme showed that all 116 tested Stolbur phytoplasma strains from Serbia belong to tuf type II variant. For further analyses, 39 Stolbur strains were selected out of 116 detected and two strains from grapevine from Croatia were also included in analyses as tuf type I reference strains to gain a larger picture of variability of groEL gene in Stolbur phytoplasmas