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Thin polymer films of block copolymers and blend/nanoparticle composites
Full text linkIn this thesis, atomic force microscopy (AFM), transmission electron
microscopy (TEM) and optical microscopy techniques were used to investigate
systematically the self-assembled nanostructure behaviour of two different types of
spin-cast polymer thin films: poly(isoprene-b-ethylene oxide), PI-b-PEO diblock
copolymers and [poly(9,9-dioctylfluorene-co-benzothiadiazole)]:poly[9,9-
dioctyfluorene-co-N-(4-butylphenyl)-diphenylamine], F8BT:TFB conjugated
polymer blends. In the particular case of the polymer blend thin films, the
morphology of their composites with cadmium selenide (CdSe) quantum dot (QD)
nanoparticles was also investigated. For the diblock copolymer thin films, the
behaviour of the nanostructures formed and the wetting behaviour on mica, varying
the volume fraction of the PEO block (fPEO) and the average film thickness was
explored. For the polymer blend films, the effect of the F8BT/TFB blend ratio (per
weight), spin-coating parameters and solution concentration on the phase-separated
nanodomains was investigated. The influence of the quantum dots on the phase
separation when these were embedded in the F8BT:TFB thin films was also
examined.
It was found that in the case of PI-b-PEO copolymer thin films, robust
nanostructures, which remained unchanged after heating/annealing and/or ageing,
were obtained immediately after spin coating on hydrophilic mica substrates from
aqueous solutions. The competition and coupling of the PEO crystallisation and the
phase separation between the PEO and PI blocks determined the ultimate
morphology of the thin films. Due to the great biocompatible properties of the PEO
block (protein resistance), robust PEO-based nanostructures find important
applications in the development of micro/nano patterns for biological and biomedical
applications.
It was also found that sub-micrometre length-scale phase-separated domains
were formed in F8BT:TFB spin cast thin films. The nanophase-separated domains of
F8BT-rich and TFB-rich areas were close to one order of magnitude smaller (in the
lateral direction) than those reported in the literature. When the quantum dot
nanoparticles were added to the blend thin films, it was found that the QDs prefer to
lie in the F8BT areas alone. Furthermore, adding quantum dots to the system, purer
F8BT and TFB nano-phase separated domains were obtained. Conjugated polymer
blend thin films are excellent candidates for alternatives to the inorganic
semiconductor materials for use in applications such as light emitting diodes and
photovoltaic cells, mainly due to the ease of processing, low-cost fabrication and
mechanical flexibility. The rather limited optoelectronic efficiency of the organic
thin films can be significantly improved by adding inorganic semiconducting
nanoparticles
Λεπτές πολυμερείς μεμβράνες συμπολυμερών κατά συστάδες και σύνθετων μιγμάτων/νανοσωματιδίων
No full textIn this thesis, atomic force microscopy (AFM), transmission electron microscopy (TEM) and optical microscopy techniques were used to investigate systematically the self-assembled nanostructure behaviour of two different types of spin-cast polymer thin films: poly(isoprene-b-ethylene oxide), PI-b-PEO diblock copolymers and [poly(9,9-dioctylfluorene-co-benzothiadiazole)]:poly[9,9- dioctyfluorene-co-N-(4-butylphenyl)-diphenylamine], F8BT:TFB conjugated polymer blends. In the particular case of the polymer blend thin films, the morphology of their composites with cadmium selenide (CdSe) quantum dot (QD) nanoparticles was also investigated. For the diblock copolymer thin films, the behaviour of the nanostructures formed and the wetting behaviour on mica, varying the volume fraction of the PEO block (fPEO) and the average film thickness was explored. For the polymer blend films, the effect of the F8BT/TFB blend ratio (per weight), spin-coating parameters and solution concentration on the phase-separated nanodomains was investigated. The influence of the quantum dots on the phase separation when these were embedded in the F8BT:TFB thin films was also examined. It was found that in the case of PI-b-PEO copolymer thin films, robust nanostructures, which remained unchanged after heating/annealing and/or ageing, were obtained immediately after spin coating on hydrophilic mica substrates from aqueous solutions. The competition and coupling of the PEO crystallisation and the phase separation between the PEO and PI blocks determined the ultimate morphology of the thin films. Due to the great biocompatible properties of the PEO block (protein resistance), robust PEO-based nanostructures find important applications in the development of micro/nano patterns for biological and biomedical applications. It was also found that sub-micrometre length-scale phase-separated domains were formed in F8BT:TFB spin cast thin films. The nanophase-separated domains of F8BT-rich and TFB-rich areas were close to one order of magnitude smaller (in the lateral direction) than those reported in the literature. When the quantum dot nanoparticles were added to the blend thin films, it was found that the QDs prefer to lie in the F8BT areas alone. Furthermore, adding quantum dots to the system, purer F8BT and TFB nano-phase separated domains were obtained. Conjugated polymer blend thin films are excellent candidates for alternatives to the inorganic semiconductor materials for use in applications such as light emitting diodes and photovoltaic cells, mainly due to the ease of processing, low-cost fabrication and mechanical flexibility. The rather limited optoelectronic efficiency of the organic thin films can be significantly improved by adding inorganic semiconducting nanoparticles.Στην παρούσα διπλωματική εργασία, χρησιμοποιήθηκαν τεχνικές μικροσκοπίας ατομικής δύναμης (AFM), ηλεκτρονικής μικροσκοπίας μετάδοσης (TEM) και οπτικής μικροσκοπίας για τη συστηματική διερεύνηση της αυτοσυναρμολογούμενης συμπεριφοράς νανοδομής δύο διαφορετικών τύπων λεπτών υμενίων πολυμερούς spin-cast: πολυ(ισοπρένιο-β-αιθυλενοξείδιο), συμπολυμερή PI-b-PEO diblock και [πολυ(9,9-διοκτυλοφθορενο-συν-βενζοθειαδιαζόλη)]:p oly[9,9-dioctyfluorene-co-N-(4-butylphenyl)-diphenylamine], F8BT:TFB συζευγμένα πολυμερή μείγματα. Στη συγκεκριμένη περίπτωση του μείγματος πολυμερών λεπτών υμενίων, διερευνήθηκε επίσης η μορφολογία των σύνθετων υλικών τους με νανοσωματίδια σεληνιδίου καδμίου (CdSe) quantum dot (QD). Για τις λεπτές μεμβράνες συμπολυμερούς diblock, διερευνήθηκε η συμπεριφορά των σχηματιζόμενων νανοδομών και η συμπεριφορά διαβροχής στον μαρμαρυγία, μεταβάλλοντας το κλάσμα όγκου του μπλοκ PEO (fPEO) και το μέσο πάχος φιλμ. Για τις μεμβράνες μείγματος πολυμερών, διερευνήθηκε η επίδραση της αναλογίας μείγματος F8BT/TFB (ανά βάρος), των παραμέτρων επικάλυψης σπιν και της συγκέντρωσης διαλύματος στις νανοπεριοχές διαχωρισμένες φάσεις. Εξετάστηκε επίσης η επίδραση των κβαντικών κουκκίδων στον διαχωρισμό φάσεων όταν αυτές ενσωματώθηκαν στις λεπτές μεμβράνες F8BT:TFB. Διαπιστώθηκε ότι στην περίπτωση λεπτών υμενίων συμπολυμερούς PI-b-PEO, ισχυρές νανοδομές, οι οποίες παρέμειναν αμετάβλητες μετά τη θέρμανση/ανόπτηση και/ή τη γήρανση, ελήφθησαν αμέσως μετά την επικάλυψη με στυψίματα σε υδρόφιλα υποστρώματα μαρμαρυγίας από υδατικά διαλύματα. Ο ανταγωνισμός και η σύζευξη της κρυστάλλωσης της ΠΕΟ και ο διαχωρισμός φάσεων μεταξύ των μπλοκ ΠΕΟ και ΠΙ καθόρισαν την τελική μορφολογία των λεπτών υμενίων. Λόγω των μεγάλων βιοσυμβατών ιδιοτήτων του μπλοκ PEO (αντοχή στις πρωτεΐνες), οι ισχυρές νανοδομές με βάση το PEO βρίσκουν σημαντικές εφαρμογές στην ανάπτυξη μικρο/νανο προτύπων για βιολογικές και βιοϊατρικές εφαρμογές. Διαπιστώθηκε επίσης ότι σχηματίστηκαν περιοχές διαχωρισμένες φάσεις κάτω από μικρόμετρα σε λεπτές μεμβράνες F8BT: TFB spin cast. Οι περιοχές που διαχωρίζονται σε νανοφάσεις των πλούσιων σε F8BT και TFB περιοχών ήταν σχεδόν μία τάξη μεγέθους μικρότερες (στην πλευρική κατεύθυνση) από αυτές που αναφέρονται στη βιβλιογραφία. Όταν τα νανοσωματίδια quantum dot προστέθηκαν στις λεπτές μεμβράνες ανάμειξης, διαπιστώθηκε ότι τα QD προτιμούν να βρίσκονται μόνο στις περιοχές F8BT. Επιπλέον, προσθέτοντας κβαντικές κουκκίδες στο σύστημα, αποκτήθηκαν καθαρότερες περιοχές διαχωρισμένες με νανοφάσεις F8BT και TFB. Οι λεπτές μεμβράνες συζευγμένου πολυμερούς μείγματος είναι εξαιρετικοί υποψήφιοι για εναλλακτικές λύσεις στα ανόργανα υλικά ημιαγωγών για χρήση σε εφαρμογές όπως δίοδοι εκπομπής φωτός και φωτοβολταϊκά στοιχεία, κυρίως λόγω της ευκολίας επεξεργασίας, της χαμηλού κόστους κατασκευής και της μηχανικής ευελιξίας. Η μάλλον περιορισμένη οπτοηλεκτρονική αποτελεσματικότητα των οργανικών λεπτών υμενίων μπορεί να βελτιωθεί σημαντικά με την προσθήκη ανόργανων ημιαγώγιμων νανοσωματιδίων
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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