Study on the performance of an XRF arrangement using Monte Carlo simulation code

Η παρούσα Διπλωματική Εργασία ασχολείται με θέματα τα οποία εμπίπτουν στη μελέτη της τεχνικής φθορισμού των ακτίνων-Χ (X-Ray Fluorescence analysis-XRF), τεχνικής που εφαρμόζεται ευρέως στο Εργαστήριο του τομέα Πυρηνικής Τεχνολογίας του Εθνικού Μετσόβιου Πολυτεχνείου (ΕΠΤ-ΕΜΠ). Στόχος αυτής της ΔΕ είναι η μελέτη της τεχνικής XRF μέσω υπολογιστικής προσομοίωσης με χρήση του κώδικα Monte-Carlo PENELOPE. Καθώς τα τελευταία χρόνια γίνονται προσπάθειες βελτιστοποίησης της τεχνικής, η εν λόγω προσέγγιση θα μπορούσε να αποτελέσει εφαλτήριο για περαιτέρω ανάπτυξη.The present Diploma Thesis deals with subjects that fall under the study of X-Ray Fluorescence analysis (XRF), a technique that is widely applied in the Nuclear Engineering Department of the National Technical University of Athens (NED-NTUA). The main aim of this thesis is the study of XRF analysis through computational simulation with the use of the code Monte-Carlo PENELOPE. As many efforts have been made during the past few years to optimize the technique, this approach could act as a springboard for further development.Σπυρίδων Σ. Χαυλή

Breakdown of spatial coding and interneuron synchronization in epileptic mice

Temporal lobe epilepsy causes severe cognitive deficits, but the circuit mechanisms remain unknown. Interneuron death and reorganization during epileptogenesis may disrupt the synchrony of hippocampal inhibition. To test this, we simultaneously recorded from the CA1 and dentate gyrus in pilocarpine-treated epileptic mice with silicon probes during head-fixed virtual navigation. We found desynchronized interneuron firing between the CA1 and dentate gyrus in epileptic mice. Since hippocampal interneurons control information processing, we tested whether CA1 spatial coding was altered in this desynchronized circuit, using a novel wire-free miniscope. We found that CA1 place cells in epileptic mice were unstable and completely remapped across a week. This spatial instability emerged around 6 weeks after status epilepticus, well after the onset of chronic seizures and interneuron death. Finally, CA1 network modeling showed that desynchronized inputs can impair the precision and stability of CA1 place cells. Together, these results demonstrate that temporally precise intrahippocampal communication is critical for spatial processing