Μελέτη λύσεων στο πρόβλημα της κάλυψης φράγματος σε Ασύρματα Δίκτυα Αισθητήρων

Τα Ασύρματα Δίκτυα Αισθητήρων (Wireless Sensor Networks - WSN), έχουν γνωρίσει τεράστια εξέλιξη τα τελευταία δέκα χρόνια και αποτελούν μία περιοχή με μεγάλη ερευνητική δραστηριότητα. Ωστόσο, λόγω κάποιων από τις ιδιαιτερότητές τους, οι κόμβοι ενός ΑΔΑ υπόκεινται σε λειτουργικούς και σχεδιαστικούς περιορισμούς, που δημιουργούν νέες προκλήσεις και αντικείμενα έρευνας με σκοπό τη βελτιστοποίηση της απόδοσης καθώς και της διάρκειας ζωής του δικτύου. Οι ιδιαιτερότητες των δικτύων αυτών δημιουργούν νέα πεδία εφαρμογής, όπως για παράδειγμα ιατρικά, επιστημονικά και επιχειρηματικά πεδία. Αξιοποιούνται, λοιπόν, με επιτυχία σε κάθε είδους εφαρμογές όπως και σε αυτές της ασφάλειας. Η κάλυψη φράγματος αποτελεί ένα από τα πιο κρίσιμα ζητήματα στα ΑΔΑ για τις εφαρμογές ασφάλειας που έχουν ως στόχο τον εντοπισμό των εισβολέων που προσπαθούν να εισέρθουν σε προστατευόμενες περιοχές. Παρ’ όλα αυτά, είναι δύσκολο να επιτευχθεί η επιθυμητή κάλυψη φράγματος μετά από την αρχική τυχαία παράταξη των αισθητήρων επειδή η τοποθεσία τους δεν μπορεί να ελεγχθεί ή να προβλεφθεί. Αντικείμενο της διπλωματικής εργασίας είναι η παρουσίαση αλγορίθμων που βελτιώνουν την ποιότητα της κάλυψης φράγματος τόσο όσον αφορά την καλύτερη κάλυψη μίας περιοχής όσο και την καλύτερη ενεργειακή απόδοση των ίδιων των αισθητήρων. Επιπλέον, οι αλγόριθμοι αυτοί κατατάσσονται με βάση τα πεδία εφαρμογής τους καθώς και με βάση τα μοναδικά τους χαρακτηριστικά. Τέλος, γίνεται αναφορά σε ποια χαρακτηριστικά ενός αλγορίθμου πρέπει να δίνεται προσοχή, τις σχεδιαστικές τους αρχές καθώς και τι επιπλέον θα μπορούσαν οι αλγόριθμοι αυτοί να υποστηρίζουν για το μέλλον.Wireless Sensor Networks (WSN) have seen a tremendous development over the last ten years and they are a region of great research activity. However, because of some of their peculiarities, the nodes of an WSN are subject to functional and design constraints that create new challenges and research objects to optimize performance and network life. The peculiarities of these networks create new fields of application, such as medical, scientific and business fields. They are therefore successfully used in all kinds of security applications. Barrier coverage is one of the most critical issues in security planning applications for detecting invaders attempting to enter protected areas. However, it is difficult to achieve the desired barrier coverage after the initial random alignment of the sensors because their location cannot be controlled or predicted. The aim of the diploma thesis is to present algorithms that improve the quality of barrier coverage both in terms of better area coverage and better energy efficiency of sensors themselves. In addition, these algorithms are ranked according to their application domains and their unique characteristics. Finally, reference is made to which features of an algorithm should be given attention, their design principles as well as what additional these algorithms could support for the future

Diffuse Goiter and Severe Hypothyroidism due to Metastasis to the Thyroid

Despite the fact that the thyroid is a highly vascularized organ, clinically significant metastatic spread to the thyroid is considered uncommon. Hypothyroidism due to these metastases seldom occurs. A 68-year-old female patient came to our department because of rapid enlargement of the lower anterior part of the neck, which developed within 2 months. She had a history of poorly differentiated esophageal adenocarcinoma diagnosed 4 years ago, for which she underwent surgical removal of the neoplasm and received three cycles of chemotherapy. On physical examination, the clinical diagnosis was hypothyroidism with large, diffuse, firm goiter, and enlarged firm and fixed cervical lymph nodes. Thyroid and cervical ultrasound examination revealed significant diffuse enlargement of the thyroid, which was heterogeneous and hypoechogenic without focal lesions and multiple pathologically enlarged cervical lymph nodes. Laboratory examination revealed increased TSH levels with decreased free T4 and T3 levels. Fine needle aspiration biopsy of the thyroid revealed a metastatic adenocarcinoma. Our patient received external beam radiation therapy and chemotherapy, but unfortunately she passed away 4 months after diagnosis. Therefore, in case of a new (focal or diffuse) lesion in the thyroid gland in a patient with a history of malignant disease, regardless of the time elapsed since the diagnosis of the primary neoplasm, relapse of the preexisting disease must be considered until proven otherwise

Zoogeography of ants on the Aegean Islands

Contains fulltext : 144967.pdf (Publisher’s version ) (Closed access

TrickVOS: A Bag of Tricks for Video Object Segmentation

Space-time memory (STM) network methods have been dominant in semi-supervised video object segmentation (SVOS) due to their remarkable performance. In this work, we identify three key aspects where we can improve such methods; i) supervisory signal, ii) pretraining and iii) spatial awareness. We then propose TrickVOS; a generic, method-agnostic bag of tricks addressing each aspect with i) a structure-aware hybrid loss, ii) a simple decoder pretraining regime and iii) a cheap tracker that imposes spatial constraints in model predictions. Finally, we propose a lightweight network and show that when trained with TrickVOS, it achieves competitive results to state-of-the-art methods on DAVIS and YouTube benchmarks, while being one of the first STM-based SVOS methods that can run in real-time on a mobile device.Comment: Accepted to ICIP 202

Spatiotemporal control of actomyosin contractility by MRCKβ signaling drives phagocytosis

Phagocytosis requires actin dynamics, but whether actomyosin contractility plays a role in this morphodynamic process is unclear. Here, we show that in the retinal pigment epithelium (RPE), particle binding to Mer Tyrosine Kinase (MerTK), a widely expressed phagocytic receptor, stimulates phosphorylation of the Cdc42 GEF Dbl3, triggering activation of MRCKβ/myosin-II and its coeffector N-WASP, membrane deformation, and cup formation. Continued MRCKβ/myosin-II activity then drives recruitment of a mechanosensing bridge, enabling cytoskeletal force transmission, cup closure, and particle internalization. In vivo, MRCKβ is essential for RPE phagocytosis and retinal integrity. MerTK-independent activation of MRCKβ signaling by a phosphomimetic Dbl3 mutant rescues phagocytosis in retinitis pigmentosa RPE cells lacking functional MerTK. MRCKβ is also required for efficient particle translocation from the cortex into the cell body in Fc receptor-mediated phagocytosis. Thus, conserved MRCKβ signaling at the cortex controls spatiotemporal regulation of actomyosin contractility to guide distinct phases of phagocytosis in the RPE and represents the principle phagocytic effector pathway downstream of MerTK

Differentiation and Transplantation of Embryonic Stem Cell-Derived Cone Photoreceptors into a Mouse Model of End-Stage Retinal Degeneration

The loss of cone photoreceptors that mediate daylight vision represents a leading cause of blindness, for which cell replacement by transplantation offers a promising treatment strategy. Here, we characterize cone differentiation in retinas derived from mouse embryonic stem cells (mESCs). Similar to in vivo development, a temporal pattern of progenitor marker expression is followed by the differentiation of early thyroid hormone receptor β2-positive precursors and, subsequently, photoreceptors exhibiting cone-specific phototransduction-related proteins. We establish that stage-specific inhibition of the Notch pathway increases cone cell differentiation, while retinoic acid signaling regulates cone maturation, comparable with their actions in vivo. MESC-derived cones can be isolated in large numbers and transplanted into adult mouse eyes, showing capacity to survive and mature in the subretinal space of Aipl1−/− mice, a model of end-stage retinal degeneration. Together, this work identifies a robust, renewable cell source for cone replacement by purified cell suspension transplantation

Antioxidant and lipid supplementation improve the development of photoreceptor outer segments in pluripotent stem cell-derived retinal organoids

The generation of retinal organoids from human pluripotent stem cells (hPSC) is now a well-established process that in part recapitulates retinal development. However, hPSC-derived photoreceptors that exhibit well-organized outer segment structures have yet to be observed. To facilitate improved inherited retinal disease modeling, we determined conditions that would support outer segment development in maturing hPSC-derived photoreceptors. We established that the use of antioxidants and BSA-bound fatty acids promotes the formation of membranous outer segment-like structures. Using new protocols for hPSC-derived retinal organoid culture, we demonstrated improved outer segment formation for both rod and cone photoreceptors, including organized stacked discs. Using these enhanced conditions to generate iPSC-derived retinal organoids from patients with X-linked retinitis pigmentosa, we established robust cellular phenotypes that could be ameliorated following adeno-associated viral vector-mediated gene augmentation. These findings should aid both disease modeling and the development of therapeutic approaches for the treatment of photoreceptor disorders

Biogas dry reforming over Ni/LnOx-type catalysts (Ln = La, Ce, Sm or Pr)

Ni/LnOx-type catalysts (Ln = La, Ce, Sm or Pr, denoted as LNO, CNO, SNO and PNO, respectively) were prepared via a citrate sol-gel method, characterized, and evaluated for the dry reforming of biogas. For the calcined catalysts, the formation of LaNiO3 perovskite crystallites with high purity was observed in the case of La, whereas NiO-LnOx mixed oxides were obtained for the other lanthanides. The reduction treatment led to the formation of medium-sized (∼15 nm) and highly dispersed Ni nanoparticles in LNO following the decomposition of the LaNiO3 perovskite, in contrast to the other catalysts, where bigger Ni crystallites were formed (∼30 nm). As a result, LNO was shown to possess a higher catalytic activity in comparison to the other materials. Regarding the catalytic stability, LNO displayed a considerable activity loss followed by a high pressure drop due to reactor blockage, meaning that the use of Sm (Ni/Sm2O3) can be considered as an alternative strategy to restrict catalyst deactivation. As evidenced by the characterization of the spent catalysts, the deactivation for the most part can be attributed to the extensive coke deposition over the catalysts. The coke deposited was found to be both in the form of more disordered/amorphous carbon, as well as in the form of highly crystalline and multi-walled carbon nanotubes.The authors gratefully acknowledge the Ministry of Science and Technology (MOST) of the People's Republic of China providing funds through the National Key Research and Development Program (project code:2017YFE013330). The authors also gratefully acknowledge that this research has been co-financed by the European Union and Greek national funds under the call “Greece – China Call for Proposals for Joint RT&D Projects” (Project code: T7DKI-00388). V.S. acknowledges the assistance of the Laboratorio de Microscopias Avanzadas-LMA-ICTS ELECMI, Universidad de Zaragoza, Spain. CIBER-BBN is an initiative funded by the VI National R&D&i Plan 2008–2011 financed by the Instituto de Salud Carlos III with the assistance of the European Regional Development Fund.Peer reviewe

Rescue of mutant rhodopsin traffic by metformin-induced AMPK activation accelerates photoreceptor degeneration

Protein misfolding caused by inherited mutations leads to loss of protein function and potentially toxic ‘gain of function’, such as the dominant P23H rhodopsin mutation that causes retinitis pigmentosa (RP). Here, we tested whether the AMPK activator metformin could affect the P23H rhodopsin synthesis and folding. In cell models, metformin treatment improved P23H rhodopsin folding and traffic. In animal models of P23H RP, metformin treatment successfully enhanced P23H traffic to the rod outer segment, but this led to reduced photoreceptor function and increased photoreceptor cell death. The metformin-rescued P23H rhodopsin was still intrinsically unstable and led to increased structural instability of the rod outer segments. These data suggest that improving the traffic of misfolding rhodopsin mutants is unlikely to be a practical therapy, because of their intrinsic instability and long half-life in the outer segment, but also highlights the potential of altering translation through AMPK to improve protein function in other protein misfolding diseases