The Maximum Rooted Connected Expansion problem

Η θεωρία γραφημάτων έχει πολλές εφαρμογές στον σύγχρονο κόσμο. Η μελέτη μας σε αυτήν συνέπεσε με ένα ενδιαφέρον πρόβλημα που ονομάζεται προανάκληση. Η προανάκληση αποτελεί ένα πολύτιμο εργαλείο για το στόχο της αποτελεσματικής πλοήγησης στο διαδύκτιο. Ένα σημαντικό ζήτημα στην προανάκληση είναι η ανταλλαγή μεταξύ του ποσού των πόρων του δικτύου που χάνονται από την προανάκληση και το κέρδος του χρόνου. Για παράδειγμα, στον ιστό, τα προγράμματα περιήγησης ενδέχεται να κατεβάζουν εκ των προτέρων έγγραφα, ενώ ένας διαδικτυακός χρήστης πλοηγείται στο διαδίκτυο. Δεδομένου ότι ο διαδικτυακός χρήστης ακολουθεί τους υπερσυνδέσμους με έναν απρόβλεπτο τρόπο, η επιλογή των ιστοσελίδων που πρέπει να προανακλήθουν πρέπει να υπολογιστεί ηλεκτρονικά. Το ερώτημα είναι τότε να προσδιοριστεί το ελάχιστο ποσό των πόρων που χρησιμοποιούνται από την προανάκληση, που εξασφαλίζει ότι όλα τα έγγραφα που έχει πρόσβαση ο διαδικτυακός χρήστης, έχουν προηγουμένως φορτωθεί στην κρυφή μνήμη. Από την άποψη αυτή, η προανάκληση μπορεί να διαμορφωθεί ως συνδυαστικό παιχνίδι δύο παικτών. Με γνώμονα τα παραπάνω οι Λάμπρου και συνεργάτες θεώρησαν το ακόλουθο πρόβλημα μεγιστοποίησης στο οποίο αναφέρονται ως πρόβλημα Maximum Rooted Connected Expansion (πρόβλημα της μέγιστης ριζικής συνεκτικής επέκτασης), MRCE που είναι NP-Hard. Με βάση ένα γράφημα G και έναν κόμβο ρίζας v 0 , θέλουμε να βρούμε ένα υποσύνολο κορυφών S που να ειναι συνδεδεμένο, να περιέχει το v 0 και να μεγιστοποιείται ο λόγος N [S ]/|S|, όπου το N [S ] δηλώνει την κλειστή γειτονιά του S , δηλαδή περιέχει όλους τους κόμβους του S και όλους τους κόμβους του S με τουλάχιστον έναν γείτονα . Αναλύουμε περαιτέρω την προσέγγισή τους σχετικά με τον τρόπο επίλυσης αυτού του προβλήματος μέσω ενός προσεγγιστικού αλγόριθμου. Μελετήσαμε άλλα σημαντικά προβλήματα στη θεωρία των γραφημάτων και τα ειδικά προβλήματά τους για να κατανοήσουμε τη δομή και τη σχέση μεταξύ όλων αυτών και του MRCE. Ως αποτέλεσμα αυτής της μελέτης χαρτογραφήσαμε αυτά τα προβλήματα σύμφωνα με τη σύνδεσή τους και την αλληλεπίδραση μεταξύ τους. Η συνεισφορά μας είναι ένας άπληστος αλγόριθμος για το MRCE που πιστεύουμε μέσω της πειραματικής μας ανάλυσης θα μπορούσε ενδεχομένως να οδηγήσει σε ένα καλό προσεγγιστικό αποτέλεσμα.Graph theory has many applications in modern world. Our study on it crossed paths with an intresting problem called Prefetching. Prefetching constitutes a valuable tool toward the goal of effiecient Web Surfing. An important issue in prefetching is the tradeoff between the amount of network’s resources wasted by the prefetching and the gain of time. For instance, in the Web, browsers may download documents in advance while a Web surfer is surfing on the Web. Since the Web surfer follows the hyperlinks in an unpredictable way, the choice of the Web pages to be prefetched must be computed online. The question is then to determine the minimum amount of resources used by prefetching that ensures that all documents accessed by the Web surfer have previously been loaded in the cache. In this regard, prefetching can be modeled as a two-player combinatorial game. Motivated by the above Sigalas et al. considered the following maximization problem to which they refer to as the Maximum Rooted Connected Expansion (MRCE) problem which is NP-hard. Given a graph G and a root node u 0 , we wish to find a subset of vertices S such that S is connected, S contains u 0 and the ratio N [S ]/|S| is maximized, where N [S ] denotes the closed neighbourhood of S , that is N [S ] contains all nodes in S and all nodes with at least one neighbour in S . We further discuss their approach on the way of solving this problem through an approximation algorithm. We studied other significant problems on graph theory like Connected Dominating Set, Maximum Leaf Spanning Tree and their special case problems so as to understand the structure and connection between all those and MRCE. As result of that study we mapped those problems according to their connection and interaction between them. Our contribution is a greedy algorithm for the MRCE which we believe through our experimental analysis could eventually lead to a small approximation, result

Ankylosing Spondylitis in a 33- years old man with Hypermobility Joints

Background: Ankylosing spondylitis, is a chronic inflammatory autoimmune disease that mainly affects spine joints. It can cause severe, chronic pain, spine fusion and chronic disability. Ehlers-Danlos syndrome is a rare heterogenous group of hereditary connective tissue disorders which are characterized by skin hyperextensibility, joint hypermobility and tissue fragility.Case report: A 33-year old man was admitted to the Rheumatology Department of 251 Airforce General Hospital in order to decide on his capability to serve his duty as an aircraftsman at Hellenic Airforce. He was diagnosed with ankylosing spondylitis twelve years ago. On physical examination joint hypermobility and skin hyperextensibility were observed and after further investigation, he was diagnosed with hypermobility type of Ehlers Danlos Syndrome. Laboratory investigation was normal. MRI radiologic investigation revealed bony sclerosis of the left sacroiliac joint and bone marrow oedema on right sacroiliac joint. No extraskeletal manifestations were detected. The patient was informed about both conditions and he was given medical advice about their proper management. Conclusion: Rare diseases sometimes manifest as atypical inflammatory arthritis syndromes. Careful medical history, thorough physical examination and use of diagnostic criteria are useful in such patients for disease identification and treatment

Ανάπτυξη Οργανοκαταλυτικών Μεθοδολογιών για τη Σύνθεση Βιοδραστικών Ενώσεων

Η Οργανοκατάλυση αποτελεί ένα σύγχρονο και ταχέως αναπτυσσόμενο τομέα κατάλυσης. Τα τελευταία χρόνια γίνονται όλο και περισσότερες προσπάθειες στον επιστημονικό κλάδο για χρήση ήπιων και οικολογικών οξειδωτικών μέσων, με σκοπό την ανάδειξη της Πράσινης Χημείας. Το Εργαστήριο Οργανικής Χημείας του Εθνικού και Καποδιστριακού Πανεπιστημίου Αθηνών, ύστερα από μια σειρά μελετών, έχει καθιερώσει ένα νέο γενικό οργανοκαταλυτικό πρωτόκολλο οξείδωσης, χρησιμοποιώντας την 2,2,2-τριφθορομέθυλο ακετοφαινόνη ως καταλύτη και το υπεροξείδιο του υδρογόνου ως οξειδωτικό. Στην παρούσα διατριβή παρουσιάζεται η χρήση της συγκεκριμένης μεθόδου για την ανάπτυξη one-pot αντιδράσεων με σκοπό τον σχηματισμό χρήσιμων ενώσεων στην Οργανική Σύνθεση. Πιο συγκεκριμένα επετεύχθη: • H σύνθεση Ο-άλλυλο υδροξυλαμινών μέσω οξείδωσης τριτοταγών αλλυλικών αμινών ακολουθούμενη από σιγματροπική μετάθεση. • H βελτιστοποίηση συνθηκών της εκλεκτικής οξείδωσης της ανιλίνης σε αζοξυβενζόλιο ή νιτροβενζόλιο. • H σύνθεση ινδολινών, πυρρολιδινών, τετραϋδροφουρανίων, 2-οξαζινών και διυδρο-οξαζολίων μέσω εποξείδωσης διπλών δεσμών. • H διυδροξυλίωση ολεφινών. • H εύρεση βέλτιστων συνθηκών σύνθεσης α-υδρόξυ σίλυλο προστατευμένης ή ελεύθερης ακετοφαινόνης μέσω οξείδωσης σιλυλοενολοαιθέρων. Επιπλέον, αναπτύχθηκε μία γενική μέθοδος σύνθεσης 2-οξοαμιδίων που φέρουν αμινοπροστατευμένο αμινοτελικό άκρο, με απώτερο τη σύνθεση αναστολέων ενζύμων.Organocatalysis constitutes a new, fast moving and expanding field in Organic Chemistry. In recent years, more efforts are made towards the use of mild and environmentally safe oxidants. The Organic Chemistry Laboratory of the National and Kapodistrian University of Athens has introduced an organocatalytic oxidation method, employing 2,2,2-trifluoromethyl acetophenone as the organocatalyst and hydrogen peroxide as the green oxidant. This thesis presents the expansion of this method in the introduction of one-pot reactions for the synthesis of high molecular complexity and useful compounds in Organic Synthesis. More specifically, we present: • An one-pot synthesis of O-allylhydroxylamines through the organocatalytic oxidation of tertiary allylic amines followed by a [2,3]-Meisenheimer rearrangement • The optimization ofthe reaction conditions for the selective oxidation of aniline to azoxybenzene or nitrobenzene. • The synthesis of indolines, pyrrolidines, tetrahydrofurans, 2-oxazines and dihydro-oxazoles by epoxidation of olefins followed by ring closing reactions. • The green dihydroxylation of olefins. • The optimization of the reaction conditions for the synthesis of protected and non-protected α-hydroxy substituted ketones via the oxidation of silylenol ethers. Furthermore, a general procedure for the synthesis of 2-oxoamides has been developed, aiming at the design and synthesis of new potential inhibitors of enzymes

THE USE OF UPPER LIMB PROSTHESIS OPTIMIZES LONG JUMP APPROACH KINEMATICS: A CASE STUDY OF AN ELITE T47 ATHLETE

This study aimed to investigate approach run kinematics using an upper limb prosthesis. A European Τ47 long- and triple- jump champion with right upper-limb congenital deficiency was analyzed in simulated approach run-ups wearing prosthesis (PW) or not (NP). Two attempts in each condition were recorded (300 fps). Step characteristics and kinematic parameters were extracted for the deficient (DLS) and intact (HLS) sides with a 2D-DLT analysis during the early (EA) and late (LA) approach. Results revealed systematic asymmetry for step frequency and length in NP, with the latter reduced in PW. Horizontal velocity in both EA and LA was larger by 0.3 m/s in PW than NP. These results suggest that asymmetry of NP reduces approach run performance compared to PW

Anthocyanin content and composition in four red winegrape cultivars (Vitis vinifera L.) under variable irrigation

Aim: The aim of this study was to determine and compare anthocyanin content and profile under variable irrigation regimes in four red grape cultivars (Vitis vinifera L.), the Greek indigenous cvs. Agiorgitiko and Xinomavro, alongside Syrah and Grenache noir. Methods and results: Three irrigation treatments were applied in a 6-year-old vineyard comprising all four varieties in a block design, starting at bunch closure (E-L 32) through harvest of 2012 and 2013: full irrigation (FI) at 100% of crop evapotranspiration (ETc), deficit irrigation (DI) at 50% of ETc and non-irrigated (NI). The identification of the compounds was performed by HPLC. Results showed that, under the hot summer conditions of the Greek climate, the four cultivars had a similar response regarding vigor and yield parameters, with values increasing with water supply. Anthocyanin concentration was maximized under non-irrigated conditions in all cultivars, but anthocyanin profile and relative distribution of individual anthocyanins among irrigation treatments showed a strong cultivar effect. Conclusion: Xinomavro seemed to favor the synthesis of more stable forms of anthocyanins under limited water supply (acylated over non-acylated and tri-oxygenated & methoxylated on the B-ring over di-oxygenated & hydroxylated) while Agiorgitiko had an opposite behavior, which might imply a need for a different irrigation strategy. Significance and impact of the study: To the best of our knowledge, this is the first comparative report of anthocyanin composition and profile in berry skin, under contrasting water status, for the two most important red winegrapes of Greece

Behaviours and beliefs related to whistleblowing against doping in sport: a cross-national study

Background: Whistleblowing has been recognized as an important deterrent of doping in elite competitive sport. The present study examined athletes’ knowledge of external whistleblowing channels and on how and where to report doping misconduct, perceived trust in different whistleblowing reporting channels, whistleblowing behaviour and athletes’ reasons for reporting (or not) doping misconduct. Methods: Athletes from Greece (n = 480), the Russian Federation (n = 512) and the United Kingdom (n = 171) completed a structured questionnaire on demographics, knowledge of different whistleblowing channels, perceived trust in internal and external whistleblowing channels, past whistleblowing behaviour and reasons for reporting (or not) doping misconduct. Results: The British athletes reported greater awareness of whistleblowing reporting channels (e.g., WADA’s Speak Up and IOC’s reporting platform) than did athletes from Greece (all p < 0.001) and Russia (p = 0.07, and p = 0.012) respectively. However, British athletes reported the lowest scores on knowledge of how and where to report doping misconduct, as compared to athletes from Greece and Russia. The majority of respondents reported greater trust to their coach or a club manager than to other whistleblowing channels, however, responses regarding other channels varied by country. Among athletes who detected doping misconduct 62% of athletes did not report it, while 38% reported it. Reasons for and against reporting doping misconduct reflected in eight themes that were identified using thematic analysis. Conclusion: Athletes showed low awareness of external whistleblowing channels and they predominantly trusted internal whistleblowing channels. Sportspersonship, confidence in resources and personal benefits were among the reasons that facilitate reporting doping misconduct. The present findings indicate that cultural context may play a role in the ways athletes perceive whistleblowing, and this should be taken into account by future interventions to promote the reporting of doping misconduct

Children’s first experience of taking anabolic-androgenic steroids can occur before their 10th birthday: a systematic review identifying 9 factors that predict doping among young people

Taking performance-enhancing drugs (PEDs) can cause serious and irreversible health consequences, which can ultimately lead to premature death. Some young people may take PEDs without fully understanding the ramifications of their actions or based on the advice from others. The purpose of this systematic review was to identify the main factors that predicted doping among young people. The literature was systematically reviewed using search engines, manually searching specialist journals, and pearl growing. Fifty-two studies, which included 187,288 young people aged between 10 and 21 years of age, 883 parents of adolescent athletes, and 11 adult coaches, who were interviewed regarding young athletes, were included in this review. Nine factors predicted doping among young people: gender; age; sports participation; sport type; psychological variables; entourage; ethnicity; nutritional supplements’ and health harming behaviors. In regards to psychological variables, 22 different constructs were associated with doping among young people. Some psychological constructs were negatively associated with doping (e.g., self-esteem, resisting social pressure, and perfectionist strivings), whereas other were positively associated with doping (e.g., suicide risk, anticipated regret, and aggression). Policy makers and National Anti-Doping Organisations could use these findings to help identify athletes who are more at risk of doping and then expose these individuals to anti-doping education. Based on the current findings, it also appears that education programs should commence at the onset of adolescence or even late childhood, due to the young age in which some individuals start doping

Whistleblowing against Doping Misconduct in Sport: A Reasoned Action Perspective with a Focus on Affective and Normative Processes

Whistleblowing against doping misconduct represents an effective deterrent of doping use in elite competitive sport. The present study assessed the effects of social cognitive variables on competitive athletes’ intentions to report doping misconduct. A second objective was to assess whether the effects of social norms on whistleblowing intentions were mediated by actor prototype evaluations and group identification and orientation. In total, 1,163 competitive athletes from Greece, Russia, and the United Kingdom completed a questionnaire on demographics, past behavior, social cognitive variables, and intentions toward whistleblowing. Regression analyses showed that whistleblowing intentions were associated with different social cognitive variables in each country. Multiple mediation modeling showed that attitudes and subjective norms were associated with whistleblowing intentions indirectly, via the effects of anticipated negative affect and group identification and orientation, respectively. The findings of this study are novel and have important implications about the social, cognitive, and normative processes underlying decision making toward reporting doping misconduct