Join-Reachability Problems in Directed Graphs

For a given collection G of directed graphs we define the join-reachability graph of G, denoted by J(G), as the directed graph that, for any pair of vertices a and b, contains a path from a to b if and only if such a path exists in all graphs of G. Our goal is to compute an efficient representation of J(G). In particular, we consider two versions of this problem. In the explicit version we wish to construct the smallest join-reachability graph for G. In the implicit version we wish to build an efficient data structure (in terms of space and query time) such that we can report fast the set of vertices that reach a query vertex in all graphs of G. This problem is related to the well-studied reachability problem and is motivated by emerging applications of graph-structured databases and graph algorithms. We consider the construction of join-reachability structures for two graphs and develop techniques that can be applied to both the explicit and the implicit problem. First we present optimal and near-optimal structures for paths and trees. Then, based on these results, we provide efficient structures for planar graphs and general directed graphs

Mobile consultant: Evaluation of additional services

As the need for mobility in the medical world increases, newer systems and applications came to light; many of them based on wireless and mobile networks. PDA based systems were presented in the past, capable of videoconferencing and transmitting high quality images between a roaming consultant and a fixed point in the hospital. These systems not only had desirable characteristics but also incorporated additional services that were found of value: paging, Voice over IP calling, Internet, email, intranet, patient record update, etc. This paper presents an engineering and clinical evaluation of those additional services based on both objective and subjective criteria. It concludes that such complementary services can be desirable as they increase personnel mobility, utilize the hospital resources more efficiently while at the same time increase productivity and decrease the cost of hardware and communications

Mobile consultant: Combining total mobility with constant access

Minimizing the time required for a medical consultant to offer his/her expert opinion, can be viewed as a life-saving procedure. We have designed and tested an integrated system that will allow a medical consultant to freely move either within, or outside the hospital, while still maintaining constant contact with the patients via videoconferencing and high-resolution imaging. The above system is explained in this paper, along with its advantages and its potential limitations. Conclusively, we demonstrate that such a system further increases the mobility of the medical consultant, while improving the healthcare service

PDA-based system for monitoring electromagnetic signals

The development of a mobile system for receiving, storing, and displaying electromagnetic-signals (EM) at specific frequencies using mobile devices and wireless networks, is of extreme interest, especially when the final means of display is a PDA, a very light and compact handheld device. In the present study, an application is developed for remote monitoring of EM-signals preceding seismic events. The particular advantages and challenges faced when developing such application are explained and future work in this area is presented

Impaired hemodynamics and neural activation? A fMRI study of major cerebral artery stenosis

Functional MRI motor mapping was performed in two women with unilateral high-grade stenosis of the middle cerebral artery (MCA) to determine the influence of impaired hemodynamics on the blood oxygenation level dependent (BOLD) response. In both patients no structural lesions were present in primary motor pathways. A redistribution of the motor network to the healthy hemisphere was the main indicator of chronic hemodynamic compromise

A smartphone-based Teleradiology system

The development of a teleradiology application for remote monitoring and processing of patient image data using 2nd generation mobile devices with enhanced network services, is of extreme interest, especially when the final means of display is a smartphone, a very light and compact handheld device. In the following paper the development of applications, that are responsible for remote monitoring and processing of medical images, is investigated

LATE-AND POST-ALPINE TECTONIC EVOLUTION OF THE SOUTHERN PART OF THE ATHOS PENINSULA, NORTHERN GREECE

To όριο μεταξύ των εσωτερικών Ελληνίδων και της Ελληνικής ενδοχώρας αποκαλύπτεται στο νότιο τμήμα της χερσονήσου του Άθω ως μια επαφή ΒΑ-ΝΔ παράταξης μεταξύ της Σέρβο μακεδόνικης μάζας και της Περιροδοπικής Ζώνης. Μελετήθηκαν τα κύρια τεκτονικά χαρακτηριστικά και η παραμόρφωση της περιοχής κατά τη διάρκεια της τελική αλπικής ορογένεσης όσο και μετά από αυτήν με σκοπό την καλύτερη κατανόηση των τελικών ορογενετικών διεργασιών που οδήγησαν στην σημερινή διαμόρφωση αυτού του ορίου. Η υπαίθρια έρευνα έδειξε ότι οι κυρίαρχες δομές στο νότιο τμήμα της χερσονήσου του Αθω είναι ένα ασύμμετρο, βυθιζόμενο προς τα ΝΑ, με φορά προς τα ΒΑ μέγα-αντίμορφο και μια ΒΑ-ΝΔ διεύθυνσης αριστερόστροφη διατρητική ζώνη. Αυτές οι δομές είναι αποτέλεσμα μιας transpressional παραμόρφωσης που άρχισε τουλάχιστον από το Ηώκαινο σε πλαστικές, συμμεταμορφικές (χαμηλή πρασινοσχιστολιθική φάση) συνθήκες και σταδιακά άλλαξε κατά το Ολιγόκαινο - Κάτω Μειόκαινο σε θραυσιγενείς συνθήκες με Α-Δ διεύθυνσης ανάστροφα ρήγματα-επωθήσεις και ΒΒΑ-ΝΝΑ διεύθυνσης δεξιόστροφα και ΒΑ-ΝΑ διεύθυνσης αριστερόστροφα ρήγματα οριζόντιας μετατόπισης. Αυτή η παραμόρφωση σβήνει κατά το Μέσο Μειόκαινο και αλλάζει σε transtension με Α-Δ διεύθυνσης αριστερόστροφα ρήγματα οριζόντιας μετατόπισης και ΒΑ-ΝΑ δεξιόστροφα πλάγια έως κανονικά ρήγματα. Από το Ανω Μειόκαινο ένα εφελκυστικό καθεστώς κυριαρχεί στην περιοχή με τον ελάχιστο κύριο άξονα τάσης (σ3) σε ΒΑ-ΝΔ διεύθυνση κατά το Άνω Μειόκαινο - Πλειόκαινο και σε Β-Ν διεύθυνση από το Κάτω Πλειστόκαινο — σήμερα.The boundary between Internal Hellenides and the Hellenic hinterland is exposed in the southern part of the Athos peninsula as a NE-SW trending contact between the Serbomacedonian massif and the Circum-Rhodope Belt. The main tectonic features and deformation of the area during late- and post-alpine times have been investigated in order to understand better the late orogenic processes that led to the present arrangement of this boundary. The field study showed that the prevailing structures in the southern Athos peninsula are an asymmetric, SW-plunging, NWverging mega-scale antiform and a NE-SW striking left-lateral shear zone. These structures are the result of a transpressional deformation that initiated at least since the Eocene under ductile, syn-metamorphic (low-greenschist fades) conditions and progressively changed during the Oligocene-Early Miocene to brittle conditions with E-W striking reverse faults-thrusts and NNW-SSE striking right-lateral and NESW striking left-lateral strike-slip faults. This deformation waned in Middle Miocene changing to transtension with E- W striking, left-lateral strike-slip and NW-SE rightlateral oblique to normal faults. Since the Late Miocene an extensional regime dominates the area with the least principal stress axis (σ3) orientated NE-SW during Late Miocene - Pliocene andN-Sfrom Early Pleistocene -presen