1,864 research outputs found

    Preparations for the Mu3e experiment: Magnet commissioning, beamline studies and a study of fake tracks

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    The Mu3e experiment at the Paul Scherrer Institute in Switzerland will search for the rare decay of a positive muon to two positrons and one electron. Phase I of the experiment aims for a sensitivity of one in 10^15 muon decays and Phase II aims for a sensitivity of one in 10^16 muon decays which is four orders of magnitude better that previous experiments. The Standard Model process via a neutrino loop is suppressed to unobservable levels O(< 10^50) and does not play a practical role. Therefore, any measurement of this decay would be a clear sign of new physics. To achieve its goal, Mu3e relies on a high rate of muons being detected in a spectrometer with a wide kinematic acceptance, excellent momentum and vertex resolutions and precise timing information. As of September 2021, data taking is expected to begin in 2022 at a muon rate of 10^8 μ/s. The full rate of 2x10^9 μ/s will not be reached before 2026. The main subject of this thesis is the preparations for the experiment which include the magnet commissioning, a magnet simulation, beamline simulation studies, beam measurements at the πE5 beamline and an analysis of fake tracks in simulation

    Median nerve’s loop in the arm penetrated by a superficial brachial artery: case report and neurosurgical considerations

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    Median nerve is commonly formed by the union of the lateral and medial cord of the brachial plexus, which embrace the third part of the axillary artery. Formation of a median nerve’s loop is a very rare condition. We present a cadaveric case, in which the right median nerve was found at the upper arm forming a fusiform neural loop penetrated by a superficial brachial artery, which continued over the forearm as the radial artery. The literature concerning nerve loops and traversing arteries is discussed, as well as the relevant embryology. We consider that such nerve loops constitute vulnerable sites of the nerve trunk since it is compressed by the pulsation of the abnormal traversing artery. Moreover, neurosurgeons should keep in mind that in case of existing arterial variation, variation of the associated neural structures may co-exist

    Operator algebras associated with C *-dynamical systems and C *-correspondences

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    Η παρούσα διπλωματική εργασία αποσκοπεί στο να περιγράψει συγκεκριμένες άλγεβρες τελεστών που σχετίζονται με C*-δυναμικά συστήματα και C*-αντιστοιχίες. Εισάγουμε την έννοια του σταυρωτού γινομένου μιας C*-άλγεβρας με μια διακριτή ομάδα και περιγράφουμε αναλυτικά την ειδική περίπτωση που η διακριτή ομάδα είναι οι ακέραιοι. Δίνουμε ικανές και αναγκαίες συνθήκες στην περίπτωση όπου η C*-άλγεβρα είναι η άλγεβρα συνεχών συναρτήσεων ενός συμπαγούς Hausdorff τοπολογικού χώρου, ώστε το σταυρωτό γινόμενο να είναι απλή C*-άλγεβρα. Επιπλέον, εισάγουμε την έννοια του ημι-σταυρωτού γινομένου και δίνουμε εναλλακτικές περιγραφές της νόρμας του στην περίπτωση που το C*-δυναμικό σύστημα επάγεται από *-αυτομορφισμό. Επίσης, εισάγουμε την έννοια της C*-αντιστοιχίας και των αναπαραστάσεων της και αποδεικνύουμε το Gauge-Invariance Uniqueness Theorem. Τέλος, χρησιμοποιούμε αποτελέσματα και εργαλεία που έχουμε αναπτύξει στα προηγούμενα κεφάλαια ώστε να αποδείξουμε ότι το C*-envelope του ημι-σταυρωτού γινομένου είναι το σταυρωτό γινόμενο, στην περίπτωση C*-δυναμικού συστήματος που επάγεται από *-αυτομορφισμό και ότι το C*-envelope της Tensor algebra μιας C*-αντιστοιχίας είναι η Cuntz-Pimsner algebra.The aim of the present thesis is to describe certain operator algebras associated with C*-dynamical systems and C*-correspondences. We introduce the notion of the crossed product of a C*-algebra by a discrete group and we study in detail the case of the integers. We give necessary and sufficient conditions, when the C*-algebra is the algebra of continuous functions on a compact Hausdorff topological space, for the crossed product to be simple. Furthermore, we introduce the notion of the semi-crossed product and we give alternative descriptions of its norm when the C*-dynamical system is induced by a ∗-automorphism. In addition, we study C*-correspondences and their representations and we prove the Gauge-Invariance Uniqueness theorem. Finally, we use results and tools that we have developed so far, in order to identify the C*-envelope of the semi-crossed product and the C*-envelope of the tensor algebra of a C*-correspondence

    Bartonella and intraocular inflammation: a series of cases and review of literature

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    Chris Kalogeropoulos1, Ioannis Koumpoulis1, Andreas Mentis2, Chrisavgi Pappa1, Paraskevas Zafeiropoulos1, Miltiadis Aspiotis11Department of Ophthalmology, Medical School, University of Ioannina, Greece; 2Laboratory of Medical Microbiology, Hellenic Pasteur Institute, Athens, GreecePurpose: To present various forms of uveitis and/or retinal vasculitis attributed to Bartonella infection and review the impact of this microorganism in patients with uveitis.Methods: Retrospective case series study. Review of clinical records of patients diagnosed with Bartonella henselae and Bartonella quintana intraocular inflammation from 2001 to 2010 in the Ocular Inflammation Department of the University Eye Clinic, Ioannina, Greece. Presentation of epidemiological and clinical data concerning Bartonella infection was provided by the international literature.Results: Eight patients with the diagnosis of Bartonella henselae and two patients with B. quintana intraocular inflammation were identified. Since four patients experienced bilateral involvement, the affected eyes totaled 14. The mean age was 36.6 years (range 12&amp;ndash;62). Uveitic clinical entities that we found included intermediate uveitis in seven eyes (50%), vitritis in two eyes (14.2%), neuroretinitis in one eye (7.1%), focal retinochoroiditis in one eye (7.1%), branch retinal vein occlusion (BRVO) due to vasculitis in one eye (7.1%), disc edema with peripapillary serous retinal detachment in one eye (7.1%), and iridocyclitis in one eye (7.1%). Most of the patients (70%) did not experience systemic symptoms preceding the intraocular inflammation. Antimicrobial treatment was efficient in all cases with the exception of the case with neuroretinitis complicated by anterior ischemic optic neuropathy and tubulointerstitial nephritis.Conclusion: Intraocular involvement caused not only by B. henselae but also by B. quintana is being diagnosed with increasing frequency. A high index of suspicion is needed because the spectrum of Bartonella intraocular inflammation is very large. In our study the most common clinical entity was intermediate uveitis.Keywords: Bartonella, neuroretinitis, intermediate uveitis, retinal vascular occlusio

    Κοινωνικά Κινήματα: Η περίπτωση των Κίτρινων Γιλέκων.

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    Η παρούσα μελέτη αποτελεί την προσπάθεια εκπόνησης της Πτυχιακής Εργασίας του προπτυχιακού προγράμματος σπουδών του Τμήματος «Πολιτικής Επιστήμης και Δημόσιας Διοίκησης» του Καποδιστριακού Πανεπιστημίου Αθηνών. Πρόκειται για μελέτη περίπτωσης του κοινωνικού κινήματος των Κίτρινων Γιλέκων, που δραστηριοποιείται στη Γαλλία από τον Νοέμβριο του 2018. Οι διαδηλώσεις και οι δράσεις του κινήματος ξέσπασαν, αρχικώς, στα περίχωρα της Γαλλίας βγάζοντας χιλιάδες ανθρώπους στους δρόμους. Αφορμή αποτέλεσε ένα πακέτο μέτρων σχετικά με την αύξηση της φορολόγησης της κατανάλωσης καυσίμων κίνησης. Πολύ σύντομα, οι διαδηλώσεις μετεξελίχθηκαν σε ένα κίνημα κατά της ίδιας της γαλλικής κυβέρνησης και των πολιτικών που προωθεί. Άνθρωποι από όλες, σχεδόν, τις γαλλικές πόλεις βγαίνουν κάθε Σάββατο στους δρόμους με πλακάτ και αντιμετωπίζουν τις ισχυρές αστυνομικές δυνάμεις. Σημαντικό για τη μελέτη παρουσιάζεται το πλαίσιο δραστηριοποίησης του κινήματος, ενώ αφιερώνεται ιδιαίτερος χώρος για τη μελέτη της ίδιας της οργάνωσης του κινήματος όσο και της προβολής του από τα ΜΜΕ. Η βαθύτερη κατανόηση του φαινομένου των Κίτρινων Γιλέκων και η προσπάθεια να εξαχθούν ορισμένες υποθέσεις για τη σχέση του κινήματος με θεσμοθετημένες μορφές εξουσίας αποτελούν πυλώνες της εν λόγω μελέτης. Επιπλέον, μέσα από την αφήγηση βασικών γεγονότων επιχειρείται η επιβεβαίωση ορισμένων θεωρητικών σχημάτων από τη σχετική βιβλιογραφία των κοινωνικών κινημάτων.This study is conducted in the frame of the Bachelor’s program of the faculty of Political Sciences and Public Administration of the National and Kapodistrian University of Athens. Actually, it is a case study of the French social movement, called “Yellow Vests”. In November 2018, the Yellow Vests started their demonstrations in the non urban areas of France and they were spread in the whole country. The cause of the burst of the French people was the announcement of the raise of diesel and petroleum prices. Shortly, the Yellow Vests were demonstrating against Macron’s government and its political agenda. Since November 2018, every Saturday people from all over France wear their yellow vest and face the police’s forces. According to the study, the frame of the actions of the social movement seems quite interesting. Moreover, the exposure of the demonstrators worldwide by the mass media can be seen critically. What are the Yellow Vests? Which is their relationship with Macron’s government and mass media? Why the Yellow Vests reject any correlation with parties or NGOs? In this study we are going to assume some answers to all of these questions

    Electroretinogram changes before and after silicone oil removal in eyes with macula-off rhegmatogenous retinal detachment

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    Background: Pars plana vitrectomy (PPV) with silicone oil (SO) injection for rhegmatogenous retinal detachment (RRD) repair may adversely affect electroretinographic responses. This study was aimed at assessing retinal function using electrodiagnostic testing after successful PPV with SO tamponade in the eyes with macula-off RRD. Methods: In this interventional comparative study, eligible participants were recruited prospectively over 1 year. We included the eyes that underwent a single successful three-port PPV with SO tamponade for the primary repair of macula-off RRD. Full-field electroretinogram (ffERG) and multifocal electroretinogram (mfERG) were recorded 1 day before and 3 days after SO removal. The amplitude and implicit time of the a- and b-waves for ffERG and P1 and N1 waves for mfERG were evaluated. The unaffected fellow eyes of the patients were selected as controls. Results: We included the ten eyes of ten patients (seven men and three women) with a mean (standard deviation) age of 58.8 (6.2) years. The mean (SD) interval between the diagnoses of macula-off RRD and PPV was 11.7 (3.6) days. The mean (SD) duration of SO tamponade was 147.8 (34.9) days. Using ffERG, significantly lower a- and b-wave amplitudes were found in the eyes before and after SO removal or compared to the unaffected fellow eyes (all P &lt; 0.05). Using the mfERG, treated eyes had significantly lower P1 amplitudes in the central R1+R2+R3 rings and in the R4 and-R5 peripheral rings of the macular area in the eyes before and after SO removal or compared to the unaffected fellow eyes (all P &lt; 0.05). The wave implicit time in ffERG and mfERG did not differ significantly in the eyes before and after SO removal or compared to the unaffected fellow eyes (all P &gt; 0.05). Conclusions: The electrical retinal response density in ERG waveforms increased following SO removal, indicating amelioration of the electrical activity of the retina and macula. These results indicate that the adverse effects of SO tamponade on electroretinography responses may be reversible with removal. In addition, ffERG and mfERG can be used to monitor retinal function in the eyes with macula-off RRD and SO tamponade. Further clinical trials are required to verify the preliminary findings of this study

    Η Διαχείριση Υπηρεσιών Πληροφορικής ( ITSM ) και η εφαρμογή του πλαισίου ITIL®: Η Περίπτωση της Εθνικής Τράπεζας της Ελλάδος.

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    Σκοπός της παρούσας εργασίας ήταν να ερευνήσει τα οφέλη και τις προκλήσεις της εφαρμογής του πλαισίου ITIL®, εντοπίζοντας τους παράγοντες που διευκολύνουν την εφαρμογή του, τα εμπόδια που μπορεί να παρουσιαστούν κατά την διαδικασία αυτή και τις κατευθυντήριες γραμμές που συμβάλλουν στην επιτυχία. Για τους σκοπούς της εργασίας, πραγματοποιήθηκε η μελέτη της περίπτωσης της Εθνικής Τράπεζας της Ελλάδος. Τα δεδομένα της έρευνας συλλέχθησαν μέσω συνεντεύξεων ενώ η ανάλυσή τους πραγματοποιήθηκε μέσω της μεθόδου της κωδικοποίησης. Από τα αποτελέσματα της ανάλυσης προκύπτει ότι η υιοθέτηση του πλαισίου ITIL® πραγματοποιήθηκε, κατά κύριο λόγο, ως αποτέλεσμα της ανάπτυξης ενός Συστήματος Διαχείρισης Υπηρεσιών Πληροφορικής (ΣΔΥΠ) βάσει των αρχών του προτύπου ISO/IEC 20000-1:2011, προκειμένου να είναι δυνατή η διαχείριση και η παρακολούθηση των παρεχόμενων υπηρεσιών. Κατά την εφαρμογή του πλαισίου, τα στελέχη της τράπεζας κλήθηκαν να αντιμετωπίσουν προκλήσεις και εμπόδια που παρουσιάστηκαν, με κυριότερο την αντίσταση της οργανωσιακής κουλτούρας στην αλλαγή, η οποία, μάλιστα, θεωρήθηκε ότι έφερε και υψηλό βαθμό σπουδαιότητας. Σε κάθε περίπτωση, η υιοθέτηση του πλαισίου ITIL® θεωρείται επιτυχής, κυρίως χάρη στην υποστήριξη και τη δέσμευση της ανώτερης διοίκησης αλλά και τη στήριξη και τη συνεργασία του συνόλου των εργαζομένων του οργανισμού, με τα οφέλη που προέκυψαν για τον οργανισμό να είναι πολυάριθμα. Τα αποτελέσματα της εργασίας επιβεβαιώνουν σε σημαντικό βαθμό τα ευρήματα προγενέστερων μελετών, αναφορικά με τα πλεονεκτήματα της υιοθέτησης του πλαισίου ITIL®, τα εμπόδια που παρουσιάζονται κατά την εφαρμογή του και τους κρίσιμους παράγοντες επιτυχίας αυτής.The primary aim of this thesis was to investigate the benefits and the challenges of the implementation of the ITIL® framework, by identifying the factors that facilitate its adoption, the obstacles that may arise during its adjustment and the guidelines that contribute to its success. For the purposes of the thesis, the case of National Bank of Greece was studied. Research data were collected through interviews, whereas their analysis was executed through the adoption of the coding method. Research results suggest that the adoption of the ITIL® framework was realized, mainly, as a result of the development of an Information Services Management System, according to the principles of ISO/IEC 20000-1:2011 Standard, in order to enable the management and monitoring of the provided services. During the implementation process, employees were required to face challenges, such as the organizational culture’s resistance to change, which was considered to be among the most important obstacles that raised. However, the adoption of the ITIL® framework was successful, mainly thanks to the support and commitment of top management as well as the support and cooperation of all organization’s employees and the benefits that emerged are multiple. The findings of the research support the findings of previous researches, regarding the advantages of ITIL® framework’s adoption, its challenges and the critical factors of its success

    Trip and Personal Characteristics towards the Intention to Cycle in Larnaca, Cyprus: An EFA-SEM Approach

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    Mobility is one of the most important and challenging aspects that influence climate change, air quality, and especially the quality of citizens&rsquo lives. Therefore, creating sustainable transport solutions makes way for different modes of transport such as the bicycle, which is continuously gaining more supporters, due to the health, economic, and environmental benefits that it provides. However, cyclists are facing several barriers (e.g., lack of infrastructure), a fact that keeps away commuters from using a bicycle for their daily trips. Investigating the factors that reflect on the commuters&rsquo intention to use a bicycle is a sine qua non for the promotion of sustainable mobility. Therefore, the objective of this paper is the investigation of the factors that prevent residents with low experience or with no cultural/lifestyle background in regards to cycling from cycling. The case study of the city of Larnaca (Cyprus) is deployed by exploring the socio-demographic and trip characteristics of the city&rsquo s residents and their relation with the intention to cycle. A two-step approach is developed, namely Explanatory Factor Analysis (EFA) and Structural Equation Modeling (SEM). Despite the promotion of cycling that education is attempting to do (successfully), other factors (such as age, distance, and time) appear to prevent Larnaca&rsquo s residents from cycling. Among the actions that local authorities should undertake is that of safety prevention of the vulnerable users of the road network. This group includes elderly people, who need major encouraging interventions by local policymakers and stakeholders. Document type: Articl
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