1,721,166 research outputs found
Investments in smart nano-control systems in cold supply chains
No full textFruit and Vegetable Supply Chain Management (F&V SCM) requires more intelligent technology to improve postharvest loss prevention; however, the current technology has to be improved to reduce the lead times and perishability dynamics in an intelligent F&V supply chain. This can be achieved by developing a more accurate environmental monitoring using advanced measurement techniques and by introducing new gold nanoparticle sensors (Au-NP-sensors) which would allow direct sensing of rotting or decaying. This paper presents the possibility how to measure the impact of these technologies on the management of fruit and vegetable supply chains, i.e. from packaging, warehousing to fruit and vegetable distribution, and thus improving the supply chain safety by tracking and tracing cargo and its environment. The evaluation of these new technologies is proposed through the Net Present Value approach of extended MRP models
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
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
Development of au nanoparticles by the method of ultrasonic spray pyrolysis for the detection of antibodies against SARS-CoV-2
Get PDFV doktorskem delu so predstavljene študije, eksperimentalno delo, tehnike karakterizacije, rezultati in analize, s pomočjo katerih smo potrdili hipotezo, da je možno Au nanodelce (AuND) pripravljene z metodo ultrazvočne razpršilne pirolize (USP), konjugirati s ciljnimi antigeni SARS-CoV-2 in rekombinantnim IgG, da bodo delovali v imunoserološkem hitrem testu na lateralni tok (LFIA), za potrditev potencialne prisotnosti protiteles proti virusu SARS-CoV-2. S ciljno izbranimi parametri (0,5 g/l Au, 5 l/min N2, 2,5 l/min H2) smo z USP sintetizirali AuND iz prekurzorja na osnovi zlatovega (III) klorida. AuND smo zbirali v steklenicah z demineralizirano vodo. Določili smo optimalne stabilizatorje in njihove koncentracije: 2,5 g/L PVP 40K ((C6H9NO)n) ter naknadno dodani 1 g/L trinatrijevega citrata (Na3C6H5O7) in saharoze (C12H22O11), da bi preprečili AuND aglomeracijo. Presevna elektronska mikroskopija AuND je pokazala, da so okrogli, s povprečno velikostjo okoli 50 nm in ozko velikostno porazdelitvijo, brez defektov in nizkim ZETA potencialom, 2,4 mV, pri pH 7,5. Za odstranitev vode iz suspenzije z AuND in stabilizatorji je bila uporabljena liofiliazcija, ki je bila izvedena pri naslednjih pogojih: zamrzovanje pri –40 °C, 4 h, atmosferski tlakprimarno sušenje pri +20 °C, 12 h, 1–4 Pasekundarno sušenje pri +30 °C, 33 h, 1–4 Pa. Nastali posušeni AuND so ohranili vse lastnosti, ki so potrebne za funkcijo oznak v hitrih LFIA testih: visoka površinska energija, površinska plazmonska resonanca in proste karboksilne skupine za konjugacijo.
V nadaljevanju izvajanja eksperimentov smo, da bi potrdili doktorske hipoteze, izvedli raziskavo in optimizacijo konjugacije AuND z antigenom SARS-CoV-2, ki je bodičasti protein S1 (ak 1-681), in s protitelesi na zajčji IgG (RMG03). Za določitev poteka konjugacije AuND smo uporabili posredne (gelske elektroforeze, UV-Vis, preizkus delovanja) in direktne (XPS, SIMS) metode. Rezultati so pokazali, da se med našim postopkom konjugacije, v fazah čiščenja odstranimo večinski delež PVP in saharoze, ter s tem sprostimo proste karboksilne funkcionalne skupine citratnih ionov, ki so vezani na povšini AuND. Na teh prostih mestih lahko poteče konjugacija prek prostih -NH2 skupin na proteinih. Njihovo funkcionalnost smo ovrednotili z eksperimentalnimi testiranji lastno razvitega LFIA testa. Na osnovi tega smo postavili model in mehanizem konjugacije AuND, ki predpostavlja, da poteka konjugacija z antigeni oziroma protitelesi prek tvorbe peptidnih vezi med N-koncem proteina in prostimi karboksilnimi skupinami citratnega iona, ki je vezan na površino AuND prek svojih karboksilnih skupin.
Za dodatno potrditev funkcionalizacije AuND z izbranimi biomolekulami smo v sklepnem delu doktorskega dela izvedli klinično študijo na pacientih UKC MB, ki je bila odobrena s sklepom KME RS št. 0120-148/2021/3. Rezultati študije so pokazali, da testi dosegajo visoko občutljivost (83 %) tako na vzorcih nosnega sluza kot na vzorcih seruma, slabšo specifičnost (66 % sluz, 74 % serum), visoko negativno napovedno vrednost (94 %) in slabšo pozitivno napovedno vrednost (38 % sluz, 45 % serum). S študijo smo potrdili delovanje AuND v funkciji oznak, saj so se testne in kontrolne linije v lastno razvitem LFIA hitrem testu obarvale.This doctoral thesis presents the studies, experimental work, characterisation techniques, results and analyses with the help of which we confirmed the hypothesis that it is possible to conjugate Au nanoparticles (AuNPs) prepared by the ultrasonic spray pyrolysis (USP) method with the target antigens of SARS-CoV-2 and recombinant IgG to function in a rapid lateral flow immunoserological assay (LFIA) to confirm the potential presence of antibodies against the SARS-CoV-2 virus. AuNPs were synthesised with the chosen parameters (0.5 g/l Au, 5 l/min N2, 2.5 l/min H2) from a precursor based on Au-chloride, using USP. AuNPs were collected in gas wash bottles filled with demineralized water. We determined the optimal stabilisers and their concentrations with the goal of preventing AuNPs agglomeration: 2.5 g/L PVP 40K ((C6H9NO)n), and subsequently added 1 g/L of trisodium citrate (Na3C6H5O7) and sucrose (C12H22O11). Microstructural analysis of the AuNPs showed them to be round, with sizes of around 50 nm and a narrow size distribution, without defects and with a low ZETA potential of 2.4 mV at a pH of 7.5. To remove water from the suspension with AuNPs and stabilisers, freeze-drying was used, which was carried out under the following conditions: freezing at -40 °C, 4 h, atmospheric pressureprimary drying at +20 °C, 12 h, 1-4 Pa, secondary drying at +30 °C, 33 h, 1-4 Pa. The resulting dried AuNPs retained all the properties required for their use as labels in LFIA assays: high surface energy, surface plasmon resonance, and free carboxyl groups for conjugation.
To confirm the doctoral hypothesis, we continued with the experiments and the optimisation of the conjugation process of AuNPs with the SARS-CoV-2 S1 antigen, with the S1 (ak 1-681) subunit, and with anti-rabbit IgG antibodies (RMG03). Indirect methods such as gel electrophoresis, UV-Vis and LFIA experiments, and direct methods such as XPS and SIMS, were used to determine the mechanism of AuNPs conjugation. The results showed that during our conjugation process, the majority of PVP and sucrose is removed in the purification stages, thereby releasing free carboxyl functional groups of citrate ions, which are bound on the AuNPs surface. Conjugation happens via the free -NH2 groups of proteins and the vacant carboxyl sites on the surface of AuNPs. We evaluated their functionality by testing through our own LFIA test. Based on this, we set up a model and mechanism of AuNPs conjugation, which assumes that conjugation with antigens or antibodies takes place through the formation of peptide bonds between the N terminus of the protein and the free carboxyl groups of the citrate ion, which is bound to the AuNPs surface via its carboxyl groups.
To further confirm the functionalisation of AuNPs with the selected biomolecules, in the concluding part of the doctoral thesis, we conducted a clinical study on patients of the University Medical Centre in Maribor, which was approved by The Commission of the Republic of Slovenia for Medical Ethics, with decision no. 0120-148/2021/3. The results of the study showed that the tests achieve a high sensitivity of 83% on both nasal mucus and serum samples and lower specificities of 66% (mucus) and 74% (serum), as well as a high negative predictive value of 94% and lower positive predictive values of 38% (mucus) and 45% (serum). Through the study, we confirmed the function of AuNPs as labels, with a successful staining of the test and control lines in our self-developed LFIA test
THE INFLUENCE OF STRESS STATE ON THE MICROSTRUCTURE OF ORTHODONTIC SHAPE MEMORY ALLOY NiTi
Get PDFV doktorski disertaciji je obravnavan problem vpliva večosnega napetostnega stanja na začetek in potek superelastičnega področja pri spominski zlitini Ni-Ti. Za raziskovalno delo je bila uporabljena komercialno dostopna ortodontska žica Ni-Ti z vsebnostjo 50,6 at.%Ni. V prvem delu raziskav smo izvedli karakterizacijo izbranega materiala. Določili smo transformacijske temperature Ms, Mf, As, Af, module elastičnosti, napetosti in deformacije na začetku in koncu superlastičnega področja ter analizirali mikrostrukturo v izhodnem nedeformiranem stanju. Z in-situ merjenjem električnega upora med obremenjevanjem pri enoosnem nategu na napravi za simulacijo enoosnega napetostnega stanja smo potrdili uporabnost te metode za določitev prehoda v superelastično stanje oziroma za spremljanje napetostno inducirane martenzitne fazne transformacije. Na osnovi teh rezultatov smo v drugem delu raziskav razvili napravo za simulacijo večosnega napetostnega stanja z možnostjo in situ merjenja električne upornosti in mikrotrdote. Z upogibom, torzijo ter kombinacijo torzije in upogiba smo simulirali obremenitve, ki so prisotne pri ortodontskem zdravljenju. S sočasnim merjenjem električnega upora smo za ta večosna napetostna stanja določili prehod v superelastično področje. Z analizo mikrostruktur pred in po obremenitvah smo identificirali spremembe in postavili modele razvoja mikrostrukture za različna napetostna stanja.This doctoral thesis deals with the problem of the influence of the multi-axial stress state at the beginning and end of the superelastic plateau in the Shape Memory Alloy Ni-Ti. For our research work commercially available orthodontic wire Ni-Ti was used with a content of 50,6 at.% Ni. In the first part of the research we determined the characterization of the selected material. We determined the transformation temperatures Ms, Mf, As, Af, modulus of elasticity, stress and strain at the beginning and end of the superelastic plateau, and analysed the microstructure of the output un-deformed state. With in-situ measurement of the electrical resistance during uni-axial loading on the device we simulated a uniaxial stress state, which confirmed the usefulness of this method for determination of the transition into superelastic condition or accompanying the stress-induced martensitic phase transformations. Based on these results, in the second part of the research we developed a device to simulate the multi-axial stress state with the possibility of in-situ measurement of electrical resistance and microhardness. We simulated the bending, torsion and combined torsion and bending loads which are present in orthodontic treatment. The simultaneous measurement of electrical resistance for this multi-axial stress state was defined during the transition into the superelastic area. By analysing the microstructures before and after load changes were identified and an evolution model of microstructure was erected for different stress states
Synthesis of gold nanoparticles with a modified ultrasonic spray pyrolysis
Get PDFDoktorsko delo predstavlja študije, eksperimentalno delo, tehnike karakterizacije, rezultate in analize, s katerimi je povezana sinteza čistih, okroglih, neaglomeriranih nanodelcev zlata (AuNPs) z velikostjo okoli 50 nm. V prvem delu raziskav smo sintetizirali AuNPs s konvencionalno ultrazvočno razpršilno pirolizo (USP). Za surovino smo uporabili tetrakloroaurično kislino HAuCl4(s), ki smo jo raztopili v vodi. To raztopino smo v komori z ultrazvokom razpršili v kapljice, ki jih je nosilni plin N2 prenesel v reakcijsko peč. V tej peči so potekale stopnje sinteze: izhlapevanje kapljic, toplotna dekompozicija, redukcija s plinom H2 in zgoščevanje. Nastali so AuNPs različnih oblik z velikostmi do 300 nm, pri čemer smo identificirali visoko stopnjo aglomeracije. Ker s konvencionalnim USP nismo dosegli cilja, smo postavili hipotezo, da lahko izdelamo ciljne AuNPs z modificiranim USP, kjer je cona izhlapevanja kapljic ločena od reakcijske peči, reducirni plin pa je uveden neposredno v reakcijsko peč. Za potrditev hipoteze smo z eksperimenti preučevali vplivne parametre USP-sinteze: koncentracijo Au v začetni raztopini, temperature v coni izhlapevanja kapljic in v reakcijski peči ter pretok plinov N2 in H2. S pomočjo tehnik karakterizacij (TEM, DLS, ICP) na nastalih AuNPs smo ugotovili, da pri USP-sintezi hkrati potekata dva mehanizma nastanka nanodelcev (»kapljica-v-delec«, DTP in »plin-v-delec«, GTP). Z DTP nastajajo veliki nanodelci – do 300 nm, z GTP pa majhni – do 50 nm. Kadar potekata oba mehanizma hkrati, dobimo neugodno bimodalno velikostno porazdelitev AuNPs. Na tej osnovi smo postavili model nastanka AuNPs, ki pojasnjuje, kako lahko pri USP-sintezi s spreminjanjem koncentracije Au v začetni raztopini in pretokov plinov vplivamo na DTP in GTP mehanizma nastanka v korist GTP. S ciljno izbranimi parametri (0,5 g/l Au, 4,5 l/min N2, 2,0 l/min H2) smo ustvarili pogoje za nastanek AuNPs z GTP-mehanizmom. Pri tem so nastali okrogli AuNPs z ozko velikostno porazdelitvijo (37,0 ± 5,5 nm). Tako smo potrdili pravilnost postavljenega modela in hipotezo, da lahko z modificiranim USP izdelamo AuNPs ciljnih lastnosti.This Doctoral Dissertation presents the studies, experimental work, characterization techniques, results and analyses of synthesis of very pure, spherical, unagglomerated gold nanoparticles (AuNPs), with sizes around 50 nm. In the first part of the research, the AuNPs were synthesized with conventional Ultrasonic Spray Pyrolysis (USP). For the raw material, tetrachloroauric acid HAuCl4(s) was dissolved in water. This precursor solution was then sprayed into droplets with ultrasound, and a carrier gas N2 then transported the droplets into a reaction furnace. In this furnace the AuNP synthesis stages took place: Droplet evaporation, thermal decomposition, reduction with H2 gas and densification. The resulting AuNPs had diverse shapes in sizes up to 300 nm, with a high degree of agglomeration. Because the aim was not achieved with the conventional USP, a hypothesis was proposed where the targeted AuNPs could be synthesized with a modified USP. With this modification, the droplet evaporation zone is separated from the reaction furnace and the reduction gas is introduced directly into the reaction furnace. To confirm this hypothesis we have carried out experiments in order to determine the influential parameters of USP synthesis: The concentration of Au in the precursor solution, evaporation zone temperature, reaction furnace temperature and gas flows of N2 and H2. Characterization of the obtained AuNPs has shown that 2 formation mechanisms take place in USP synthesis (Droplet-to-Particle, DTP and Gas-to-Particle, GTP). With DTP, nanoparticles up to 300 nm are formed, while smaller nanoparticles up to 50 nm are formed with GTP. When both mechanisms occur simultaneously, we obtain a bimodal size distribution of AuNPs. Based on these findings, we have set up an AuNP formation model, explaining how one can control the DTP and GTP mechanisms in USP by changing the most influential parameters, the concentration of Au in the precursor solution and the gas flows. Based on this model, parameter values were selected (0.5 g/l Au, 4.5 l/min N2, 2.0 l/min H2) to establish conditions where the AuNPs are formed only by the GTP mechanism. This has yielded spherical AuNPs in a narrow size distribution (37.0 ± 5.5 nm). Targeted AuNPs were thus synthesized, confirming the model and the hypothesis of AuNP synthesis with USP
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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