1,720,966 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Kinetics of bioethanol production with yeast Saccharomyces cerevisiae on raw sugar beet juice
No full textIstražena je dinamika ekstrakcije saharoze iz rezanaca šećerne repe vodom temperature 20, 28, 36, i 72 °C, za laminarni režim strujanja kroz ekstrakcijsku kolonu. Postavljene su polinomna i eksponencijalna jednadžba za ovisnost koncentracije šećera u ekstraktu o temperaturi i vremenu ekstrakcije. Istražen je inhibicijski učinak visokih koncentracija supstrata na rast kvasca Saccharomyces cerevisiae u anaerobnim uvjetima i eksperimentalno su određeni kinetički parametri za ukupne šećere (KS = 52,411 g/L, μMAX =0,425 h-1, KI = 122,112 g/L) i za glukozu (KS = 9,079 g/L, μMAX =0,301 h-1, KI = 36,084 g/L). Diferencijalnom metodom testiran je inhibicijski učinak koncentracije etanola [0-13 % (vol/vol)] na kinetiku rasta proizvodnog soja i određeni su kinetički parametri za tri formalno kinetička modela. Najbolje slaganje s eksperimentalnim rezultatima postignuto je modelom prema Jerusalimskom (Jerusalimsky, 1968) uz kinetičke parametre (μMAX = 0,430 h-1, KP = 2,269 g/L).The dynamics of sucrose extraction from sugar beet was investigated by using water at different temperatures (20, 28, 36, and 72 ° C) and laminar flow through the extraction column. Polynomial and exponential equations were selected to describe the relation between sugar concentration (at different extraction temperatures) and extraction time. Under anaerobic conditions, inhibitory effect of high different substrate concentrations on the growth rate of yeast Saccharomyces cerevisiae was studied. Experimentally determined kinetic parameters of these cultivations were: KS = 52,411 g/L, μMAX =0,425 h-1, KI = 122,112 g/L; and for glucose: KS = 9,079 g/L, μMAX =0,301 h-1, KI = 36,084 g/L. Furthermore, the inhibitory effect of ethanol concentration (0 - 13 % vol/vol) on anaerobic yeast cultivation was examined by differential method. For this anaerobic yeast cultivation, three formal kinetic growth models were established. On the basis of obtained results, Jerusalimsky model shows the best agreement with experimental results by following kinetic parameter values: μMAX = 0,430 h-1 and KP = 2,269 g/L
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Mathematical modelling of two-step continuous process of bioethanol production
No full textBioetanol je obnovljivi izvor energije koji se primjenjuje kao gorivo ili dodatak gorivima. U proizvodnji bioetanola jedna od najčešćih sirovina jest šećerna repa zbog visokog udjela saharoze. Za fermentaciju šećera iz šećerne repe primjenjuje se tehnološka operacija ekstrakcije. U ovom radu je provedena kontinuirana ekstrakcija i fermentacija šećera iz šećerne repe u koloni za ekstrakciju i bioreaktoru s mješalom pri različitim parametrima procesa (temperatura, vrijeme zadrţavanja i koncentracija biomase). Eksperimentalni podaci pri temperaturi 36 °C, vremenu zadržavanja od 20 min i koncentraciji biomase od 30 g/L bili su uspoređeni s vrijednostima izračunatim primjenom matematičkog modela koji je izrađen za reaktor prvog stupnja odnosno ekstrakcijsku kolonu te su pokazali relativno dobar stupanj sukladnosti, što znači da je model verbalno i matematički ispravno postavljen.Bioethanol is the renewable source of energy that can be applied as a fuel or an additive to fuels. In bioethanol production sugar beet is frequently used because of its high sucrose content. Technological operation of extraction is being used for fermentation of sugar from sugar beet. In this thesis a continuous extraction and beet sugar fermentation in extraction colon and stirred-tank bioreactor has been done under the various set of parameters (temperature, retention time and biomass concentration). Experimental data under the temperature of 36°C, retention time of 20 min and biomass concentration of 30 g/L have been compared to the values made by mathematical model application that has been made for firstdegree-reactor (extraction colon), and yet shown relatively good and degree of complementary. The model therefore has a correct verbal and mathematical background
Development of sustainable processes for bioethanol production
No full textCilj ovog doktorskog rada bio je usporediti ekstrakciju i istiskivanje plinom (eng. gas stripping) kao metode izdvajanja etanola iz fermentirane podloge. Posebno je istraženo toksično djelovanje ekstraktanata di(propilenglikol)butiletera, 1-tert-butoksipropan-2-ola, etil-oleata, oktan-1-ola i oleil alkohola na kulturu kvasca Saccharomyces cerevisiae te je raspravljena njihova moguća primjena u integriranom sustavu. Provedeno je istraživanje razdvajanja faza i stabilnosti emulzija za sustave podloga-ekstraktant. Najpogodniji plin za istiskivanje etanola izabran je temeljem rezultata istraživanja različitih plinova (zrak, dušik i ugljikov(IV) oksid) obzirom na brzinu izdvajanja etanola iz razrijeđenih vodenih otopina pri različitim prividnim srednjim linearnim brzinama strujanja plina. Istiskivanje etanola iz fermentirane podloge i iz organskog ekstrakta pomoću CO2 istraženo je pri atmosferskom tlaku i u uvjetima sniženog tlaka.The aim of this investigation was the comparison of extraction and stripping as methods of ethanol separation from fermentation broth. The toxicity of octan-1-ol, 1-tert-butoxy-propan-2-ol, di(propylene glycol) butyl ether, ethyl oleate and oleyl alcohol on the culture of the yeast Saccharomyces cerevisiae was studied. The use of examined solvents in an integrated system was discussed. The phase separation and the emulsion stability for the broth-extracting solvent system were examined. The most convenient gas for the ethanol stripping was selected by examining of different gases (air, nitrogen and carbon(IV) oxide) concerning of ethanol stripping rate (from diluted aqueous solutions) and different superficial gas velocities. Gas stripping of ethanol by CO2 as a carrier from fermented broth and organic extracts was studied under atmospheric and low-pressure conditions
Extraction of ethanol with higher alcohols in production of biogas from renewable sources
Get PDFCilj ovog diplomskog rada je istražiti primjenu viših alkohola (pentan-1-ola, oktan-1-ola, nonan-1-ola i oleil alkohola) kao ekstraktivnih otapala s visokim vrelištem za izdvajanje etanola iz fermentirane podloge u integriranom bioreaktorskom sustavu. Ekstrakcija etanola je istraživana u svrhu dobivanja ekološki, energetski i financijski učinkovitijeg procesa od uobičajeno primijenjene višestupanjske destilacije. Istraženo je toksično djelovanje ekstraktanta na kulturu kvasca Saccharomyces cerevisiae i ponašanje dvokomponentnih (ekstraktant–voda) odnosno trokomponentnih smjesa (ekstraktant-voda-etanol) te učinkovitost razdvajanja organske faze od podloge. Izrađeni su binodalni trokomponentni dijagrami za sustave pentan-1-ol/voda/etanol, oktan-1-ol/voda/etanol, nonan-1-ol/voda/etanol i oleil alkohol/voda/etanol. Na temelju binodalnih dijagrama izvršen je proračun potrebnih količina otapala za trostupanjski ekstrakcijski sustav i predložen je sustav tehnološke linije za izdvajanje etanola iz fermentirane podloge.The aim of this work was to investigate the application of higher alcohols characterized by high boiling points (i.e. pentan-1-ol, octan-1-ol, nonan-1-ol and oleyl alcohol) as extraction solvents for the ethanol extraction from broth, fermented in the integrated bioreactor system. The goal was the development of the ecologically, energetically and financially more efficient process than conventional multi-stage distillation. Applied extractants were tested for its toxicity on the Saccharomyces cerevisiae yeast culture. The behaviors of two-component systems (extractant-water) and three-component mixtures (extractant-water-ethanol) were investigated toward the efficiency of separation of organic phase (extract) and the water phase (rafinate). Binodal curves were constructed for systems: pentan-1-ol / water / ethanol, octan-1-ol / water / ethanol, nonan-1-ol / water / ethanol and oleyl alcohol / water / ethanol. Binodal diagrams were used for the calculations of required solvent amounts for the ethanol extraction in the three-stage extraction system. The plants for ethanol production based on extractions with higher alcohols were proposed
Analysis of process kinetic of PHB biosynthesis in continuous production using the cascade of 5 biorectors and electron microscopy
No full textU ovom istraživanju analiziran je peterostupanjski reaktorski sustav za kontinuiranu proizvodnju PHB-a. Korištena je skenirajuća transmisijska elektronska mikroskopija (STEM). Programski paket ImageJ primijenjen je za analizu veličine stanica i unutarstaničnih poli-(3-hidroksibutirat) (PHB) granula. Primijenjena je tehnika digitalne analize STEM snimaka uz mjerenje tlocrtne površine stanica i PHB granula (pod pretpostavkom da između površine na slici i realnog volumena objekta postoji direktna proporcionalnost). Specifične brzine rasta (μ) i specifične brzine nastajanja PHB-a (qP) za kulturu Cupriavidus necator DSM 545 određene su gravimetrijski i pomoću odnosa tlocrtnih površina stanica i PHB granula za svih pet reaktora. Dobiveni rezultati uspoređeni su međusobno. Na temelju dobivenih rezultata, zaključeno je da se ImageJ program može uspješno koristiti za određivanje veličine stanica i granula mjerenjem tlocrtne površine istih na STEM snimkama. Specifična brzina rasta (μ) određena mjerenjem tlocrtne površine stanica slaže se sa specifičnom brzinom rasta (μ) određenom gravimetrijski.In this study, a 5-step reactor system for the production of PHB was analyzed. Scanning transmission electron microscopy (STEM) and ImageJ software package were used to anaylize the cell size and the size of intracellular poly-3-hydroxybutyrate (PHB) granules. Digital imaging technique (analysis) of the STEM images was applied for the measuring of cells and PHB-granula areas (assuming that there is a direct proportionality between the image area and the related real object volume). The specific growth rate (μ) and the specific PHB productivity rate (qp) for Cupriavidus necator DSM 545 culture were determined by gravimetric and by digital imaging technique analysis for all five reactors in cascade. The results were compared mutually. Based on the obtained results, it is evident that the ImageJ software package can be successfully used for the determination of cells and PHB-granula areas present in the STEM images. The specific growth rate (μ) determined by digital imaging technique analysis matches very well with those determined by gravimetric method
Matematičko modeliranje i istraživanje prijenosa mase u razvoju održivih biotehnoloških procesa proizvodnje organskih otapala i biogoriva
No full textThe aim of this work was to explore the possibility for development of the new, low-energy demanding process for bioethanol production directly from sugar beet cossettes. For that purpose a two-stage bioreactor system was assembled where the first stage was the vertical packed-bed column in order to use the vertical column in the first stage as an extracting column filled with the packed-bed of sugar beet cossettes that were extracted with concentrated suspension of baker’s yeast thus performing simultaneous extraction and fermentation. The second stage in a bioreactor system was a stirred tank bioreactor. The extraction of sugars was studied in 0,5 and 1,0 [m] column at extractant temperature of 20, 28, 36 and 72°C, respectively, by using two different residence times 24 and 49 [min]. Non-structured mathematical models of sugar extraction process were developed using linear, nonlinear and surface response regression methods as well as by the use of ternary plots. Also, the structured compartment type mathematical model for the sugar extraction from the sugar beet cossettes was established and explored in detail. The commercial baker’s yeast was the working microorganism in the simultaneous process of extraction and fermentation of sugar beet cossettes, thus it was subjected to the thorough fermentation kinetic analysis. Based on achieved results an own formal kinetic mathematical model for microbial conversion of sugars to ethanol (containing substrate and product inhibition terms) was developed and interconnected with the structured mathematical model of extraction (convection/diffusion mass transfer). This combined mathematical model was applied for the modelling of simultaneous extraction and fermentation of sugar beet cossettes in the two step bioreactor system. The model described correctly the new bioprocess and was able to predict values of parameters that have not been able to determine experimentally in those heterogeneous systems. It was proven that the model could be additionaly improved by the use of the computational fluid dynamics calculations.Cilj ovog rada bio je razvoj novog, energetski nisko zahtjevnog procesa proizvodnje bioetanola izravno iz rezanaca šećerne repe. U tu svrhu konstruiran je dvo-stupanjski bioreaktorski sustav (sastavljen od vertikalne kolone s nasutim slojem rezanaca šećerne repe koji je podvrgnut ekstrakciji s gustom suspenzijom pekarskog kvasca s kojom je provedena simultana ekstrakcija fermentacija. Drugi stupanj u bioreaktorskom sustavu bio je bioreaktor s miješalicom. Ekstrakcija šećera istraživana je u 0,5 i 1,0 [m] dugom vertikalnom cijevnom bioreaktoru na temperaturama od 20, 28, 36 i 72°C i kod dva vremena zadržavanja 24 te 49 minuta. Nestrukturirani matematički modeli ekstrakcije šećera su razvijeni korištenjem linearne i nelinearne regresije, metodom površinske regresije te korištenjem ternarnih dijagrama. Također je uspostavljen strukturirani kaskadni matematički model za ekstrakciju šećera iz rezanaca šećerne repe koji je detaljno istražen. Pekarski kvasac je korišten kao radni mikroorganizam u postupku simultane ekstrakcije i fermentacije te je stoga podvrgnut pažljivoj analizi kinetike fermentacije. Na temelju postignutih rezultata razvijen je vlastiti formalno kinetički matematički model za mikrobnuS konverziju šećera u etanol (koji sadrži članove za inhibiciju supstratom i produktom) koji je zatim povezan je sa strukturnim modelom ekstrakcije (konvektivni prijenos mase i molekulske difuzija). Ovaj složeni matematički model i primijenjen za modeliranje procesa simultane ekstrakcije i fermentacije rezanaca šećerne repe u bioreaktorskom sustavu od dva stupnja. Model je dobro opisivao novi bioproces te je mogao predviđati vrijednosti parametara koje nije bilo moguće eksperimentalno utvrditi u takovim heterogenim sustavima. Dokazano je da se model može dodatno unaprijediti s pomoću računalne dinamike fluida
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