University of Nicosia

About: University of Nicosia is a education organization based out in Nicosia, Cyprus. It is known for research contribution in the topics: Population & Context (language use). The organization has 988 authors who have published 2765 publications receiving 30748 citations.

Graph Theoretical Characteristics of EEG-Based Functional Brain Networks in Patients With Epilepsy: The Effect of Reference Choice and Volume Conduction

Abstract: It is well-established that both volume conduction and the choice of recording reference (montage) affect the correlation measures obtained from scalp EEG, both in the time and frequency domains. As a result, a number of correlation measures have been proposed aiming to reduce these effects. In our previous work, we have showed that scalp-EEG based functional brain networks in patients with epilepsy exhibit clear periodic patterns at different time scales and that these patterns are strongly correlated to seizure onset, particularly at shorter time scales (around 3 and 5 h), which has important clinical implications. In the present work, we use the same long-duration clinical scalp EEG data (multiple days) to investigate the extent to which the aforementioned results are affected by the choice of reference choice and correlation measure, by considering several widely used montages as well as correlation metrics that are differentially sensitive to the effects of volume conduction. Specifically, we compare two standard and commonly used linear correlation measures, cross-correlation in the time domain, and coherence in the frequency domain, with measures that account for zero-lag correlations: corrected cross-correlation, imaginary coherence, phase lag index, and weighted phase lag index. We show that the graphs constructed with corrected cross-correlation and WPLI are more stable across different choices of reference. Also, we demonstrate that all the examined correlation measures revealed similar periodic patterns in the obtained graph measures when the bipolar and common reference (Cz) montage were used. This includes circadian-related periodicities (e.g., a clear increase in connectivity during sleep periods as compared to awake periods), as well as periodicities at shorter time scales (around 3 and 5 h). On the other hand, these results were affected to a large degree when the average reference montage was used in combination with standard cross-correlation, coherence, imaginary coherence, and PLI, which is likely due to the low number of electrodes and inadequate electrode coverage of the scalp. Finally, we demonstrate that the correlation between seizure onset and the brain network periodicities is preserved when corrected cross-correlation and WPLI were used for all the examined montages. This suggests that, even in the standard clinical setting of EEG recording in epilepsy where only a limited number of scalp EEG measurements are available, graph-theoretic quantification of periodic patterns using appropriate montage, and correlation measures corrected for volume conduction provides useful insights into seizure onset.

Prospective teachers’ understanding of the multiplicative part-whole relationship of fraction

Abstract: The part-whole multiplicative relationship, as a topic that gives rise to the concept of fraction, is fundamental in education at the primary school level, and must therefore be included in training courses for prospective primary school teachers (PSTs). In this paper, we introduce a first study of a larger project, which aims to understand the usefulness of a semantic triangle in studying prospective teachers’ knowledge of various mathematical topics. In particular, we present the results of a study focused in the starting level of the fraction concept, based on the multiplicative part-whole relationship. We carried out this study with PSTs by means of a questionnaire. We analyzed the collected responses using a framework of three components that form a semantic triangle, in terms of their conceptual structure, system of representations, and contexts and modes of use of the part-whole relationship. The results show different typologies of meaning expressed by the participants in terms of the semantic triangle. Each typology emphasizes some aspects of the meaning of the part-whole relationship such as the equality of parts, the model of area as representation and the context of division.

Balancing Wireless Data Broadcasting and Information Hovering for Efficient Information Dissemination

Abstract: Wireless data broadcasting is an efficient, bandwidth preserving way of data dissemination. However, as the amount of data increases, the waiting time of the clients becomes unacceptably high. The present paper proposes the combination of optimal wireless broadcasting and information hovering, as an effective means of performance improvement in vehicular networks with locality of demand. While state-of-the-art works exploit user collaboration only as a means of wireless coverage extension, the proposed scheme proposes parallel dissemination through broadcasting and user networking over the whole studied area. Optimal, periodic broadcast scheduling is adopted at the highest tier for data dissemination. At the lowest tier, users can exploit information hovering around selected anchoring points, in order to retrieve data faster than their next scheduled broadcast. The issue of sharing the dissemination load optimally between the broadcasting and the hovering subsystems is mapped to the classic pull-push balancing problem. Through analysis, the long-standing “optimal cut-off point” balancing method is shown to be suboptimal, and a new method is proposed which achieves lower client serving time in any of the cases. Simulation results in realistic VANETs show that the proposed dissemination scheme surpasses state-of-the-art works in terms of efficiency and client satisfaction.

Collagen content and extracellular matrix cause cytoskeletal remodelling in pancreatic fibroblasts.

Abstract: In many solid tumours a desmoplastic reaction takes place, which results in tumour tissue stiffening due to the extensive production of extracellular matrix (ECM) proteins, such as collagen, by stromal cells, mainly fibroblasts (FBs) and cancer-associated fibroblasts (CAFs). In this study, we investigated the effect of collagen stiffness on pancreatic FBs and CAFs, particularly on specific cytoskeleton properties and gene expression involved in tumour invasion. We found that cells become stiffer when they are cultured on stiff substrates and express higher levels of alpha-smooth muscle actin (α-SMA). Also, it was confirmed that on stiff substrates, CAFs are softer than FBs, while on soft substrates they have comparable Young's moduli. Furthermore, the number of spread FBs and CAFs was higher in stiffer substrates, which was also confirmed by Ras-related C3 botulinum toxin substrate 1 ( RAC1) mRNA expression, which mediates cell spreading. Although stress fibres in FBs become more oriented on stiff substrates, CAFs have oriented stress fibres regardless of substrate stiffness. Subsequently, we demonstrated that cells' invasion has a differential response to stiffness, which was associated with regulation of Ras homologue family member ( RhoA) and Rho-associated, coiled-coil containing protein kinase 1 ( ROCK-1) mRNA expression. Overall, our results demonstrate that collagen stiffness modulates FBs and CAFs cytoskeleton remodelling and alters their invasion properties.

Do cognitive styles of users affect preference and performance related to CAPTCHA challenges

Abstract: A Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA) is nowadays a widely used security mechanism for constructing a high-confidence proof that the entity interacting with a remote service is actually a human being. Aiming to investigate the relation among users' cognitive styles, and CAPTCHA challenges in terms of preference and performance, a study is in progress which entails a psychometric-based survey for extracting users' cognitive styles, combined with a real usage scenario with two variations of CAPTCHA mechanisms. A total of 131 participants of age between 19 and 25 participated in the reported study providing interesting insights with respect to users' cognitive styles and CAPTCHA preference and performance issues.