Egalitarian Judgment Aggregation

Egalitarian considerations play a central role in many areas of social choice theory. Applications of egalitarian principles range from ensuring everyone gets an equal share of a cake when deciding how to divide it, to guaranteeing balance with respect to gender or ethnicity in committee elections. Yet, the egalitarian approach has received little attention in judgment aggregation -- a powerful framework for aggregating logically interconnected issues. We make the first steps towards filling that gap. We introduce axioms capturing two classical interpretations of egalitarianism in judgment aggregation and situate these within the context of existing axioms in the pertinent framework of belief merging. We then explore the relationship between these axioms and several notions of strategyproofness from social choice theory at large. Finally, a novel egalitarian judgment aggregation rule stems from our analysis; we present complexity results concerning both outcome determination and strategic manipulation for that rule.Comment: Extended version of paper in proceedings of the 20th International Conference on Autonomous Agents and Multiagent Systems (AAMAS), 202

Egalitarian judgment aggregation

Egalitarian considerations play a central role in many areas of social choice theory. Applications of egalitarian principles range from ensuring everyone gets an equal share of a cake when deciding how to divide it, to guaranteeing balance with respect to gender or ethnicity in committee elections. Yet, the egalitarian approach has received little attention in judgment aggregation—a powerful framework for aggregating logically interconnected issues. We make the first steps towards filling that gap. We introduce axioms capturing two classical interpretations of egalitarianism in judgment aggregation and situate these within the context of existing axioms in the pertinent framework of belief merging. We then explore the relationship between these axioms and several notions of strategyproofness from social choice theory at large. Finally, a novel egalitarian judgment aggregation rule stems from our analysis; we present complexity results concerning both outcome determination and strategic manipulation for that rule.publishedVersio

Exploring Next-Generation Engineering Bioplastics: Poly(alkylene furanoate)/Poly(alkylene terephthalate) (PAF/PAT) Blends

Polymers from renewable resources and especially strong engineering partially aromatic biobased polyesters are of special importance for the evolution of bioeconomy. The fabrication of polymer blends is a creative method for the production of tailor-made materials for advanced applications that are able to combine functionalities from both components. In this study, poly(alkylene furanoate)/poly(alkylene terephthalate) blends with different compositions were prepared by solution blending in a mixture of trifluoroacetic acid and chloroform. Three different types of blends were initially prepared, namely, poly(ethylene furanoate)/poly(ethylene terephthalate) (PEF/PET), poly(propylene furanoate)/poly(propylene terephthalate) (PPF/PPT), and poly(1,4-cyclohenedimethylene furanoate)/poly(1,4-cycloxehane terephthalate) (PCHDMF/PCHDMT). These blends’ miscibility characteristics were evaluated by examining the glass transition temperature of each blend. Moreover, reactive blending was utilized for the enhancement of miscibility and dynamic homogeneity and the formation of copolymers through transesterification reactions at high temperatures. PEF–PET and PPF–PPT blends formed a copolymer at relatively low reactive blending times. Finally, poly(ethylene terephthalate-co-ethylene furanoate) (PETF) random copolymers were successfully introduced as compatibilizers for the PEF/PET immiscible blends, which resulted in enhanced miscibility

Thermal Decomposition Kinetics and Mechanism of In-Situ Prepared Bio-Based Poly(propylene 2,5-furan dicarboxylate)/Graphene Nanocomposites

Bio-based polyesters are a new class of materials that are expected to replace their fossil-based homologues in the near future. In this work, poly(propylene 2,5-furandicarboxylate) (PPF) nanocomposites with graphene nanoplatelets were prepared via the in-situ melt polycondensation method. The chemical structure of the resulting polymers was confirmed by 1H-NMR spectroscopy. Thermal stability, decomposition kinetics and the decomposition mechanism of the PPF nanocomposites were studied in detail. According to thermogravimetric analysis results, graphene nanoplatelets did nοt affect the thermal stability of PPF at levels of 0.5, 1.0 and 2.5 wt.%, but caused a slight increase in the activation energy values. Pyrolysis combined with gas chromatography and mass spectroscopy revealed that the decomposition mechanism of the polymer was not altered by the presence of graphene nanoplatelets but the extent of secondary homolytic degradation reactions was increased

Synthesis, Properties, and Enzymatic Hydrolysis of Poly(lactic acid)-co-Poly(propylene adipate) Block Copolymers Prepared by Reactive Extrusion

Poly(lactic acid) (PLA) is a biobased polyester with ever-growing applications in the fields of packaging and medicine. Despite its popularity, it suffers from inherent brittleness, a very slow degradation rate and a high production cost. To tune the properties of PLA, block copolymers with poly(propylene adipate) (PPAd) prepolymer were prepared by polymerizing L-lactide and PPAd oligomers via reactive extrusion (REX) in a torque rheometer. The effect of reaction temperature and composition on the molecular weight, chemical structure, and physicochemical properties of the copolymers was studied. The introduction of PPAd successfully increased the elongation and the biodegradation rate of PLA. REX is an efficient and economical alternative method for the fast and continuous synthesis of PLA-based copolymers with tunable properties

Recent Advances in Nanocomposite Materials of Graphene Derivatives with Polysaccharides

This review article presents the recent advances in syntheses and applications of nanocomposites consisting of graphene derivatives with various polysaccharides. Graphene has recently attracted much interest in the materials field due to its unique 2D structure and outstanding properties. To follow, the physical and mechanical properties of graphene are then introduced. However it was observed that the synthesis of graphene-based nanocomposites had become one of the most important research frontiers in the application of graphene. Therefore, this review also summarizes the recent advances in the synthesis of graphene nanocomposites with polysaccharides, which are abundant in nature and are easily synthesized bio-based polymers. Polysaccharides can be classified in various ways such as cellulose, chitosan, starch, and alginates, each group with unique and different properties. Alginates are considered to be ideal for the preparation of nanocomposites with graphene derivatives due to their environmental-friendly potential. The characteristics of such nanocomposites are discussed here and are compared with regard to their mechanical properties and their various applications

Synthesis and study of new bionanocomposite polymeric materials for tissue engineering applications

In the context of this PhD dissertation, bionanocomposite polymeric materials based on poly (ε-caprolactone) (PCL) were synthesized and studied in order to improve its physicochemical and biological properties. PCL is an aliphatic, biodegradable and biocompatible aliphatic polyester used primarily in biomedical applications. Apart from these attractive features, including easy moulding, 3D printing capability and good rheological properties, PCL is a bioinert polymer, which limits cell adhesion and proliferation on its surface and hence its range of applications is limited, as well as its use in high load bearing applications because of its low mechanical properties. It is a fact that a single-component scaffold cannot meet all the requirements for biomedical applications, and for this reason the scientific community has turned to composite and nanocomposite materials to solve the challenges it faces, which are increasingly demanding as medicine and technology evolve. In this context, this thesis examined the possibility of optimizing the physicochemical and biological properties of PCL in order to meet as many of the conditions required for a scaffold in tissue engineering applications as possible. Two classes of nanoparticles, aluminosilicate nanotubes and nanobioglasses of various compositions, were incorporated in the polymeric matrix PCL by in situ ring opening polymerization, as well as by spin coating. The nanoparticles were fully characterized and demonstrated remarkable physicochemical and morphological properties, while their cytotoxicity was assessed by in vitro assays. Due to the versatility of composite and nanocomposite materials with PCL, as well as their good bioactivity and biocompatibility, we can conclude that they can offer solutions in different fields of tissue engineering and regenerative medicine. Their properties can be regulated by varying the molecular weight, additive content, chemical structure and size of the additives, and the introduction of active pharmaceutical ingredients into their pore structure. The added advantage of synthetic polymeric materials against ceramics and metals is therefore the flexibility in their properties but also in their shape which can be modified by a variety of techniques. It is not random, therefore, that the international scientific community believes that new generation biomaterials are expected to be hybrid, bio-functional, intelligent and contain active ingredients. As a result, much of the research is still under way and is not yet completed in order to draw a definitive conclusion on the effect of nanoparticles on biomaterials. The combination of biodegradable polymers and nanoparticles opens up a new perspective in the development of bionanocomposites for biomedical applications with adjustable mechanical, thermal, morphological and electrical properties.Στα πλαίσια της παρούσας διδακτορικής διατριβής, συντέθηκαν και μελετήθηκαν βιονανοσύνθετα πολυμερικά υλικά με βάση την πολυ(ε-καπρολακτόνη) (PCL), με στόχο τη βελτίωση των φυσικοχημικών και βιολογικών της ιδιοτήτων. Η PCL είναι ένας αλειφατικός, βιοαποικοδομήσιμος και βιοσυμβατός αλειφατικός πολυεστέρας που χρησιμοποιείται κυρίως σε βιοϊατρικές εφαρμογές. Πέρα όμως από αυτά τα ελκυστικά της χαρακτηριστικά, που συμπεριλαμβάνουν την εύκολη μορφοποίηση, δυνατότητα 3D εκτύπωσης και καλές ρεολογικές ιδιότητες, η PCL είναι ένα βιοαδρανές πολυμερές, κάτι το οποίο περιορίζει τη προσκόλληση και τον πολλαπλασιασμό κυττάρων στην επιφάνειά του και συνεπώς και το εύρος εφαρμογών της στην ιστομηχανική, καθώς επίσης δεν μπορεί να ανταπεξέλθει σε εφαρμογές με μεγάλα μηχανικά φορτία λόγω των χαμηλών μηχανικών της ιδιοτήτων. Είναι γεγονός ότι ένα μονοφασικό ικρίωμα δεν μπορεί να ικανοποιήσει όλες τις απαιτήσεις τις εκάστοτε βιοϊατρικής εφαρμογής, και για το λόγο αυτό η επιστημονική κοινότητα έχει στραφεί στα σύνθετα και νανοσύνθετα υλικά για την επίλυση των προκλήσεων που αντιμετωπίζει, οι οποίες είναι ολοένα πιο απαιτητικές καθώς προοδεύει η Ιατρική και η Τεχνολογία. Στα πλαίσια αυτά, σε αυτή τη διδακτορική διατριβή μελετήθηκε η δυνατότητα βελτιστοποίησης των φυσικοχημικών και βιολογικών ιδιοτήτων της PCL έτσι ώστε να πληρεί όσο το δυνατόν περισσότερες από τις προϋποθέσεις που απαιτούνται για ένα ικρίωμα σε εφαρμογές ιστομηχανικής. Επιλέχθηκαν δύο κατηγορίες νανοπροσθέτων, οι αργυλοπυριτικοί νανοσωλήνες και νανοβιοϋαλοι διαφόρων συστάσεων, τα οποία ενσωματώθηκαν στη πολυμερική μήτρα PCL μέσω in situ πολυμερισμού διάνοιξης δακτυλίου καθώς και μέσω της τεχνικής της περιστροφικής συν-απόθεσης (spin coating). Τα νανοσωματίδια χαρακτηρίστηκαν πλήρως και αποδείχθηκε ότι παρουσιάζουν αξιοσημείωτες φυσικοχημικές και μορφολογικές ιδιότητες, ενώ η κυτταροτοξιτότητα τους αξιολογήθηκε με in vitro δοκιμές. Λόγω της ευελιξίας των σύνθετων και νανοσύνθετων υλικών με PCL, καθώς και της καλής τους βιοενεργότητας και βιοσυμβατότητας, μπορούμε να συμπεράνουμε ότι μπορούν να προσφέρουν λύσεις σε διάφορα πεδία της ιστομηχανικής και της αναγεννητικής ιατρικής. Οι ιδιότητες τους μπορούν να ρυθμιστούν μεταβάλλοντας το μοριακό βάρος, το περιεχόμενα σε πρόσθετα, τη χημική δομή και το μέγεθος των προσθέτων, και την εισαγωγή δραστικών φαρμακευτικών ουσιών στο πορώδες τους. Το πρόσθετο πλεονέκτημα των συνθετικών πολυμερικών υλικών έναντι των κεραμικών και των μετάλλων είναι λοιπόν αυτό, η ευελιξία δηλαδή στις ιδιότητες τους αλλά και στο σχήμα τους που μπορεί να τροποποιηθεί με μία πληθώρα τεχνικών. Δεν είναι τυχαίο λοιπόν ότι η διεθνής επιστημονική κοινότητα πιστεύει ότι τα βιοϋλικλα νέας γενιάς αναμένοται να είναι υβριδικά, βιολειτουργικά, έξυπνα και να περιέχουν δραστικά συστατικά. Ως αποτέλεσμα, μεγάλο μέρος της έρευνας εξακολουθεί να βρίσκεται σε εξέλιξη και δεν έχει ακόμη ολοκληρωθεί ώστε να εξαχθεί ένα οριστικό συμπέρασμα σχετικά με την επίδραση των νανοπροσθέτων στα βιοϋλικά. Ο συνδυασμός βιοαποικοδομήσιμων πολυμερών και νανοπροσθέτων ανοίγει νέα προοπτική στην εξέλιξη νανοσυσκευών για βιοϊατρικές εφαρμογές με ρυθμιζόμενες μηχανικές, θερμικές, μορφολογικές και ηλεκτρικές ιδιότητες

Representation Matters: Characterisation and Impossibility Results for Interval Aggregation

International audienceIn the context of aggregating intervals reflecting the views of several agents into a single interval, we investigate the impact of the form of representation chosen for the intervals involved. Specifically, we ask whether there are natural rules we can define both as rules that aggregate separately the left and right endpoints of intervals and as rules that aggregate separately the left endpoints and the interval widths. We show that on discrete scales it is essentially impossible to do so, while on continuous scales we can characterise the rules meeting these requirements as those that compute a weighted average of the endpoints of the individual intervals