WSN operability during persistent attack execution

Wireless Sensor Networks (WSNs) are utilized in a number of critical infrastructures, e.g. healthcare, disaster and relief. In sensitive environments, it is vital to maintain the operability of the network in an effort to support the decision-making process that depends on the sensors’ observations. The network’s operability can be maintained if observations can reach the specified destination and also if the sensors have adequate energy resources. The operability is negatively affected by security attacks, such as the selective forward and the denial of service (DoS), that can be executed against the WSN. The attacks’ impact greatly depends on the attackers’ capabilities such as their knowledge and the number of malicious nodes they hold. Currently, the research community focuses on addressing casual attackers that don’t persist with their attack strategy. However, the proposed solutions cannot address persistent attackers that continue with their attack execution after the network has applied appropriate recovery countermeasures. Designing an adaptive recovery strategy is challenging as a number of issues need to be taken into consideration such as the network’s density, the number of malicious nodes and the persistent attack strategy. This research work formulates a persistent attack strategy and investigates the integration of different recovery countermeasures in WSNs. The evaluation results demonstrate that an adaptive recovery strategy can enhance the network’s recovery benefits, in terms of increased packet delivery and decreased energy consumption, and prolong its operability. Moreover, the observations made are envisioned to encourage new contributions in the area of adaptive intrusion recovery in WSNs

Antibodies against endogenous retroviruses promote lung cancer immunotherapy

B cells are frequently found in the margins of solid tumours as organized follicles in ectopic lymphoid organs called tertiary lymphoid structures (TLS). Although TLS have been found to correlate with improved patient survival and response to immune checkpoint blockade (ICB), the underlying mechanisms of this association remain elusive. Here we investigate lung-resident B cell responses in patients from the TRACERx 421 (Tracking Non-Small-Cell Lung Cancer Evolution Through Therapy) and other lung cancer cohorts, and in a recently established immunogenic mouse model for lung adenocarcinoma. We find that both human and mouse lung adenocarcinomas elicit local germinal centre responses and tumour-binding antibodies, and further identify endogenous retrovirus (ERV) envelope glycoproteins as a dominant anti-tumour antibody target. ERV-targeting B cell responses are amplified by ICB in both humans and mice, and by targeted inhibition of KRAS(G12C) in the mouse model. ERV-reactive antibodies exert anti-tumour activity that extends survival in the mouse model, and ERV expression predicts the outcome of ICB in human lung adenocarcinoma. Finally, we find that effective immunotherapy in the mouse model requires CXCL13-dependent TLS formation. Conversely, therapeutic CXCL13 treatment potentiates anti-tumour immunity and synergizes with ICB. Our findings provide a possible mechanistic basis for the association of TLS with immunotherapy response

Cohomology of configuration spaces of surfaces as mapping class group representations

We express the rational cohomology of the unordered configuration space of a compact oriented manifold as a representation of its mapping class group in terms of a weight-decomposition of the rational cohomology of the mapping space from the manifold to a sphere. We apply this to the case of a compact oriented surface with one boundary component and explicitly compute the rational cohomology of its unordered configuration space as a representation of its mapping class group. In particular, this representation is not symplectic, but has trivial action of the second Johnson filtration subgroup of the mapping class group

Homology of Configuration Spaces of Surfaces as Mapping Class Group Representations

In this thesis, we study the homology of configuration spaces of surfaces viewed as representations of the mapping class group of the surface, distinguishing between various flavours: ordered and unordered configurations, of closed surfaces and surfaces with boundary, and with different homology coefficients. In Chapter 2, we prove a version of the scanning isomorphism that is “untwisted” and equivariant with the mapping class group action. We further prove that scanning remembers a product arising from superposing configurations. We apply this equivariant scanning to compute the rational cohomology of unordered configurations of surfaces with boundary. In Chapter 3, we adapt certain cellular decompositions of compactified configuration spaces to obtain the kernel of the mapping class group action on the homology of unordered configurations of both kinds of surfaces and with any coeffiecients. Finally, in Chapter 4, we geometrically construct mapping classes deep in the Johnson filtration that act non-trivially on the homology of ordered configurations, in support of a conjecture by Bianchi, Miller and Wilson

Fluid dynamics at a compliant bifurcation model

Ph.D.Don P. Gidden

Χρήση του Twitter από τα μέλη του Ελληνικού Κοινοβουλίου

Στην παρούσα εργασία διερευνάται η χρήση του μέσου κοινωνικής δικτύωσης “Twitter” από τους βουλευτές του ελληνικού κοινοβουλίου. Πραγματοποιείται, εν πρώτοις, επισκόπηση του θεωρητικού πλαισίου, το οποίο είναι αρκετά ευρύ, καθώς τα μέσα κοινωνικής δικτύωσης αποτελούν ένα σχετικά πρόσφατο πεδίο ακαδημαϊκής μελέτης. Για την έρευνα της χρήσης του Twitter από τα μέλη της ελληνικής Βουλής διενεργούνται τόσο ποσοτικές, όσο και ποιοτικές μέθοδοι. Στο πρώτο στάδιο της μελέτης υλοποιείται ποσοτική ανάλυση εκ της οποίας προκύπτει ο δείκτης ακολουθησιμότητας, και στη συνέχεια για τους 32 πιο ακολουθήσιμους βουλευτές υπολογίζεται και ο βαθμός σύμπλεξης. Οι 16 βουλευτές που συγκεντρώνουν τους μεγαλύτερους βαθμούς σύμπλεξης μελετώνται περαιτέρω στο ποιοτικό σκέλος της μελέτης. Διενεργούνται, ειδικότερα, δομημένες συνεντεύξεις, καθώς και αναλύσεις περιεχόμενου με βάση τις ετικέτες και τις αναφορές που έχουν χρησιμοποιήσει οι βουλευτές κατά το τρίμηνο 20-08-2016 έως 20-11-2016. Κύριοι στόχοι από τη διεξαγωγή της ανωτέρω έρευνας είναι να εξετασθεί τι είδους αναρτήσεις προτιμούν να αναρτούν οι Έλληνες βουλευτές, εάν και κατά πόσο αλληλεπιδρούν με τους χρήστες, καθώς και ποιες είναι οι επιδόσεις τους σε σημαντικούς δείκτες, όπως είναι η ακολουθησιμότητα και η σύμπλεξη. Οι συνεντεύξεις πραγματοποιούνται, καθώς κρίνεται ενδιαφέρον να κατανοηθεί ποια είναι και η οπτική και άποψη του ίδιου του πολιτικού προσωπικού για τα σύγχρονα μέσα επικοινωνίας και ποιοι ήταν οι πρωταρχικοί λόγοι που τους οδήγησαν να ενταχθούν στον κόσμο των μέσων κοινωνικής δικτύωσης.The present research studies the use of the social media platform “Twitter” from the members of the Greek parliament. Firstly, has been carried out an overview of the theoretical framework, which is wide, because social media is a relatively new field of academic research. In order to study the use of Twitter by the Greek politicians, quantitative as well as qualitative methods of research are being conducted. In the first part of the study a qualitative analysis is being implemented, which results to the followership index and, for the 32 parliament members with the highest followership rank, the engagement rank. The 16 politicians with the higher engagement rank are being analyzed more in the qualitative part of the research. Particularly, structured interviews (questionnaires) are being conducted, as well as content analysis which is based on the hashtags and the mentions that have been used by the parliament members during the following time period: 20/08/2016 – 20/11/2016. Main objectives of the present study is to understand what kind of tweets is more preferable by the Greek politicians, if and to what extent are interactive with other users and which is their performance at important indexes, such as the followership and the engagement. It is, moreover, interesting to know what is their own perspective and view of the modern social networks and which were the principal reasons that lead them at joining the new social media “space”

Recovering from the selective forwarding attack in WSNs - enhancing the recovery benefits of blacklisting and rerouting using directional antennas

Wireless sensor networks (WSNs) face a number of security challenges that can compromise their operation. A typical security attack that can be launched by an adversary, in order to affect the network’s communication, is the selective forwarding attack. If compromisation occurs, it is essential to recover the network to a stable state. In the context of mission-critical WSNs the challenge is not just to recover from compromisation but it is vital to restore an enhanced network operation in order to support a reliable decision-making. Sensor nodes usually address the selective forwarding attack by deploying blacklisting and rerouting. These countermeasures have been proposed in the context of omni-directional networks. This research work investigates the utilization of directional antennas in WSNs in order to increase the recovery benefits gained by the blacklisting and rerouting countermeasures in terms of reliability, survivability and responsiveness, attributes that are vital for the operation of mission-critical applications