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- PublicationΓνώσεις , Στάσεις και πρακτικές των Νοσηλευτών στην Κύπρο σχετικά με την πρόληψη και τη θεραπέια των Ελκών Πίεσης(Σχολή Θετικών Επιστημών : Τμήμα Επιστημών Υγείας : Διδακτορικό στην Νοσηλευτική, 0007-12-23)
;Λειβαδιώτης, ΑνδρόνικοςΑποστολίδου, Σταυρούλλα- ΑνδρέαΓνώσεις, Στάσεις και Πρακτικές των Νοσηλευτών στην Κύπρο σχετικά με την Πρόληψη και τη Θεραπεία των Ελκών Πίεσης Εισαγωγή: Τα έλκη πίεσης ή κατακλίσεις, όπως ονομάζονται, επηρεάζουν την ποιότητα της ζωής των ατόμων με προβλήματα κινητικότητας και θεωρούνται μείζονος σημασίας για τους νοσηλευτές, οι οποίοι εμπλέκονται ενεργά σε θέματα φροντίδας και περίθαλψης αυτών των ασθενών. Το έλκος πίεσης προκαλείται από καταστροφή του δέρματος και των υποκείμενων ιστών, που δημιουργείται ως επακόλουθο της συνεχιζόμενης ισχαιμίας των ιστών λόγω της πίεσης στο δέρμα. Τα έλκη πίεσης αποτελούν ένα συχνό φαινόμενο με γρήγορη εξέλιξη το οποίο, παράλληλα, μπορεί να δημιουργήσει επιπρόσθετα ψυχοσωματικά ή και κοινωνικά προβλήματα στον ίδιο τον ασθενή, αλλά και στο άμεσο περιβάλλον του. Σκοπός: Ο σκοπός της παρούσας έρευνας είναι να διερευνήσει γνώσεις, στάσεις και πρακτικές των νοσηλευτών στην Κύπρο σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης. Επιμέρους στόχοι: 1.Να διερευνήσει τις γνώσεις των νοσηλευτών σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης. 2.Να διερευνήσει τις στάσεις των νοσηλευτών σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης. 3.Να διερευνήσει τις πρακτικές των νοσηλευτών σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης. 4.Η δημιουργία ενός τροποποιημένου ερωτηματολογίου ως εργαλείο αξιολόγησης γνώσεων, στάσεων και πρακτικών των νοσηλευτών στην Κύπρο σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης. Μεθοδολογία: Η συλλογή των δεδομένων έγινε με τη συμπλήρωση ενός τροποποιημένου κατασκευασμένου ερωτηματολογίου που βασίστηκε στο ερωτηματολόγιο «Γνώσεις, στάσεις και πρακτικές των νοσηλευτών σχετικά με την πρόληψη και θεραπεία των ελκών από πίεση» (PU Κnowledge tool) και ο μελετώμενος πληθυσμός αποτελείτο από 1.872 νοσηλευτές που εργάζονταν σε Νοσοκομεία, Κέντρα Υγείας / Κοινοτική Νοσηλευτική και Γηροκομεία / Οίκους Ευγηρίας – Κέντρα Αποκατάστασης (Δημόσια, Ημικρατικά, Ιδιωτικά) της Κύπρου. Πρόκειται για συγχρονική περιγραφική έρευνα και η στατιστική ανάλυση πραγματοποιήθηκε στην SPSS v.28, ενώ οι στατιστικές μέθοδοι που έχουν χρησιμοποιηθεί είναι δείκτης εσωτερικής συνέπειας Cronbach’s alpha, δείκτης γραμμικής συσχέτισης Pearson r, υπολογίστηκε ο δείκτης διακριτικότητας για κάθε δήλωση γνώσεων (συσχέτιση συνολικού σκορ γνώσεων συμμετεχόντων με την ορθότητα), υπολογίστηκε ο δείκτης σημειακής διασειριακής συσχέτισης Point biserial correlation, μονομεταβλητή συσχέτιση δημογραφικών και ατομικών στοιχείων με τις Γνώσεις, Στάσεις και Πρακτικές, χρήση του independent samples Welsch-test, χρήση του ANOVA, πραγματοποιήθηκε πολυμεταβλητή ανάλυση με τη χρήση της απλής και πολλαπλής γραμμικής παλινδρόμησης. Αποτελέσματα: Ο μέσος όρος ηλικίας των συμμετεχόντων νοσηλευτών ήταν 36.0 (8.8). Τα αποτελέσματα έδειξαν ότι οι νοσηλευτές της Κύπρου έχουν μέτριο επίπεδο γνώσεων με μέσο όρο 22.8 (Τυπ. Απ. = 4.4) σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης, θετικές στάσεις με μέσο όρο 48.2 (Τυπ. Απ. = 5.8) σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης και ικανοποιητικές πρακτικές με μέσο όρο 38.2 (Τυπ. Απ. = 6.9) σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης. Ο αριθμός των νοσηλευτών που πήραν μέρος ήταν 1.872 νοσηλευτές. Οι συμμετέχουσες γυναίκες νοσηλεύτριες έχουν υψηλότερες συνολικές γνώσεις (b = 0.61, p= 0.002), στάσεις (b = 1.2, p < 0,001) και πρακτικές (b = 1.8, p < 0.001) από τους συμμετέχοντες άντρες νοσηλευτές σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης. Οι συμμετέχοντες νοσηλευτές που δεν διάβασαν ποτέ επιστημονικό άρθρο για τα έλκη πίεσης έχουν χαμηλότερο επίπεδο συνολικών γνώσεων (b = -1.6, p <0,001), στάσεων (b = -0.29, p = 0.040) και πρακτικών (b = -1.4, p = 0.040). Οι συμμετέχοντες νοσηλευτές που δεν είχαν ποτέ εκπαίδευση στα έλκη πίεσης είχαν χαμηλότερο επίπεδο γνώσεων (b = -1.8, p<0.001), στάσεων (b = -1.1, p = 0.034) και πρακτικών (b = -2.7, p < 0.001). Συμπεράσματα: Η παρούσα έρευνα κατέδειξε ότι το επίπεδο των γνώσεων των νοσηλευτών της Κύπρου για την πρόληψη και τη θεραπεία των ελκών πίεσης είναι μέτριο. Ακόμη από την παρούσα έρευνα προέκυψε ότι το επίπεδο των στάσεων των νοσηλευτών της Κύπρου για την πρόληψη και τη θεραπεία των ελκών πίεσης είναι θετικό. Επίσης η παρούσα έρευνα έδειξε ότι το επίπεδο των πρακτικών των νοσηλευτών της Κύπρου σχετικά με την πρόληψη και τη θεραπεία των ελκών πίεσης είναι ικανοποιητικό. Επιπρόσθετα, από την παρούσα έρευνα διαφάνηκε από τους νοσηλευτές της Κύπρου σημαντική διαφορά μεταξύ των δύο φύλων των συμμετεχόντων. Τα αποτελέσματα αυτά συμβαδίζουν με τα ευρήματα άλλων παρόμοιων ερευνών στη διεθνή βιβλιογραφία που δείχνουν παρόμοιο ή ίδιο επίπεδο γνώσεων, στάσεων και πρακτικών των νοσηλευτών σχετικά με την πρόληψη ή τη θεραπεία των ελκών πίεσης. - PublicationTowards the development of Intelligent Pedestrian Mobility Systems (IPMS)(0009)
;Papageorgiou, George- NathanaelMaimaris, AthanasiosIn today's highly developed traffic networks, too much emphasis is given on the development of intelligent systems for vehicles, while pedestrians/bicyclists are mainly ignored. Clearly, there is a need for effectively integrating pedestrians in the overall design of intelligent transportation systems for the sustainable development and effective utilization of urban traffic networks. Especially, with the currently available technology, a lot can be achieved in this direction. This paper reviews current technologies on their capability to be employed for increasing connectivity, conspicuity, comfort, convenience, and conviviality of urban pedestrian networks. As a result, recommendations are given for developing what we call Intelligent Pedestrian Mobility Systems (IPMS), which should be a basic ingredient for any smart city. - PublicationComputer modelling of sound fields in bounded spatial systems; extension of the ray method to curved surfaces(1/1/1997)Papageorgiou, GeorgeThis paper investigates computer simulation of sound fields in acoustical environments. All the contemporary acoustical computer models represent the room to be modelled as a series of flat or planar surfaces. Generally these surfaces must have many edge vertices but must be contained in a single plane. That means that curved walls are required to be represented by a finite number of flat planar segments. The quality of the overall simulation process is directly related to file three dimensional geometrical and acoustical model and obviously the restriction of flat surface representation is a negative factor. Further the use of a large number of planar surfaces to represent a curved wall is inefficient, since as the number of surfaces increases the number of calculations also increases. A computer model based on the ray method is suggested that is able to predict the acoustic environment of closed or partially closed spaces and to tolerate curved boundaries without approximating them into a series of flat surfaces as contemporary models do. Note that in buildings with curved walls there are often serious problems with speech intelligibility and the appreciation of music. The main applications of the proposed computer model are in relation to churches with domes, indoor sports halls with curved ceilings and generally any large enclosure of any particular geometry. Predicted results are compared with theoretical calculations and experimental measurements.
- PublicationThe role of stress in the regulation of drug metabolizing enzymes in mice(1/1/1998)
;Konstandi, Maria ;Marselos, Marios ;Radon-Camus, A. M. ;Johnson, Elizabeth O.Lang, MattiThe role of stress in the regulation of several enzymatic systems which are involved in the biotransformation of xenobiotics in the liver was investigated in this study using restraint stress as a stress model. The results demonstrated that stress suppressed total basal P450 content (35%) and basal ethoxyresorufin 7-dealkylase (EROD) activity (33%), while slightly increasing basal methoxyresorufin 7-dealkylase (MROD) activity (20%). Basal pentoxyresorufin 7- dealkylase (PROD) and coumarin 7-hydroxylase (COH) activities were not affected. On the other hand, restraint stress increased total P450 content in 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP)-treated mice (35%), while slightly suppressing PROD activity (26%). In addition, CYP2E1 dependent p-nitrophenol hydroxylation (PNP), was suppressed (40%) by stress in TCPOBOP-treated animals and cytosolic aldehyde dehydrogenases were not affected. Although stress had no effect on basal P4502A5 activity, the inducibility of this hepatic activity increased 2-fold after stress exposure. A pronounced suppression (7-fold) in glutathione content was observed in lungs of TCPOBOP treated mice after stress, whereas basal levels remained unaffected. In addition, only a slight suppression (20%) in liver glutathione content was found in both treatment groups. Northern blot analysis revealed that restraint stress had a relatively suppressive effect on control CYP1A2 expression in the liver. In contrast, stress markedly enhanced the expression of liver CYP2A5 in TCPOBOP-treated mice, but did so to a lesser extent in controls. Stress also increased CYP2A5 mRNA in TCPOBOP-treated mice to a grater degree than the activity of the corresponding cytochrome. On the other hand, liver P4502A5 activity was found to be induced by TCPOBOP by about 2.5-fold. However, the drug does not appear to be involved in the expression of CYP2A5. Finally, although the activity of liver P4502A5 cytochrome was found to be increased 3, 8 and 27 h after stress, after which it gradually declined up to 75 h, CYP2A5 liver expression appeared to be suppressed 3, 8, 27 and 51 h after stress, while 75 h later it apparently reached normal levels. In conclusion, the results of this study showed that restraint stress significantly alters several enzymatic systems differently at a basal level than under conditions of TCPOBOP induction. In addition, stress was found to significantly interfere with the expression processes of CYP1A2 and CYP2A5. - PublicationOptimization of cell configuration and comparisons using evolutionary computation approaches(1/1/1998)
; Zalzala, Ali M.S.This paper examines a cellular manufacturing optimization problem in a new facility of a pharmaceutical company. The new facility, together with the old one, should be adequate to handle current and future production requirements. The aim of this paper is to investigate the potential use of evolutionary computation in order to find the optimum configuration of the cells in the facility. The objective is to maximize the total number of batches processed per year in the facility. In addition, a two-objective optimization search was implemented, using several evolutionary computation methods. One additional objective is to minimize the overall cost, which is proportional to the number of cells in the facility. The multi-objective optimization programs were based on three approaches: The weighted-sum approach, the Pareto-optimality approach, and the Multiobjective Genetic Algorithm (MOGA) approach. - PublicationEvidence of α2-adrenoceptor involvement in B[α]P induction processes of drug-metabolizing enzymes: The effect of stress(1/1/1998)
;Konstandi, Maria ;Kostakis, Dimitris ;Johnson, Elizabeth O. ;Lang, MattiMarselos, MariosCentral to the appropriate regulation of behavioral and physiological changes induced by stress are the noradrenergic neuronal systems which have been implicated in a large number of stress-induced pathophysiological states. Endoplasmic reticulum-bound cytochromes (CYPs) play a crucial role in drug metabolism, resulting in deactivation or formation of reactive derivatives. In turn, these products may be responsible for the chemotherapeutic, mutagenic or carcinogenic properties of the parent compound. The present study assesses the effect of a specific α2- adrenoceptor agonist, dexmedetomidine (DEXT), on stress-induced modification of cytochrome activity in rats using a restraint stress model. The results indicated that activation of the α2-adrenoceptor with DEXT did not alter basal hepatic methoxyresorufin 7-dealkylase (MROD). On the other hand, it appeared to enhance MROD in benzo[a]pyrene (B[a]P) treated animals. Of interest was the finding that stress blocked DEXT-induced MROD enhancement in B[α]P- treated rats. In addition, DEXT had no effect on basal hepatic pentoxyresorufin 7-dealkylase (PROD), while it further enhanced the strong induction by B[a]P. Stress was also found to block this effect. Hepatic ethoxyresorufin 7-dealkylase (EROD) activity was strongly increased by B[a]P; this effect was enhanced by DEXT. In contrast, the DEXT enhanced induction was further strengthened by stress. These findings suggest that α2-adrenoceptors may modulate the induction of cytochromes CYP1A1, 1A2 and 2B1 by B[a]P in rats and that stress may modify this process. In particular, stress may regulate the inducibility of P4501A1 activity by B[a]P via mechanisms related to α2-adrenoceptors. - PublicationA genetic programming heuristic for the one-machine total tardiness problem(1/1/1999)
; Zalzala, Ali M.S.Genetic programming has rarely been applied to manufacturing optimisation problems. In this report we investigate the potential use of genetic programming for the solution of the one-machine total tardiness problem. Combinations of dispatching rules are employed as an indirect way of representing permutations within a modified genetic programming framework. Hybridisation of genetic programming with local search techniques is also introduced, in an attempt to improve the quality of solutions. All the algorithms are tested on a large number of benchmark problems with different levels of tardiness and tightness of due dates. - PublicationEvolving similarity coefficients for the solution of cellular manufacturing problems(1/1/2000)
; Mort, NeilThe cell formation problem is a classic manufacturing optimization problem associated with the implementation of a cellular manufacturing system. A variety of hierarchical clustering procedures have been proposed for the solution of this problem. Essential for the operation of a clustering procedure is the determination of a form of similarity between the objects that are going to be grouped. In this paper we employ a Genetic Programming algorithm for the evolution of new similarity coefficients for the solution of simple cell formation problems. Evolved coefficients are tested against the well-known Jaccard's similarity coefficient on a large number of problems taken from the literature. - PublicationNeuroendocrine manifestations in Sjogren's syndrome: Relation to the neurobiology of stress(1/1/2000)
;Johnson, Elizabeth O.Moutsopoulos, Haralampos M.Evidence suggests that autoimmune rheumatic diseases are associated with neuroendocrine dysfunction. Sjogren's syndrome (SS) is proposed as an ideal model to study perturbations in the neuroimmune axis, since patients tend to be medication free and studies are not confounded by the effects of chronic immunosuppressive therapy. The functional integrity of the adrenal, gonadal, and thyroid axes was assessed in SS. Pituitary function of the HPA axis was evaluated directly by determining the ACTH released during oCRH stimulation, while adrenal function was assessed indirectly by endogenous ACTH released during oCRH stimulation. Low basal activity of the HPA axis was associated with pituitary hyporesponsiveness to exogenous CRH, as well as hyporesponsiveness of the adrenal glands to endogenous ACTH. These findings are compatible with a central deficiency of the adrenal axis. An overall attenuated and delayed LH and FSH response to LHRH stimulation was also indicative of central dysfunction of the gonadal axis in SS. SS patients demonstrated elevated basal TSH levels and evidence of mild hypothyroidism. Basal prolactin concentrations were also elevated in SS, and both TSH and PRL showed relatively increased responses to TRH stimulation. The data suggest a central deficiency in all three neuroendocrine axes: adrenal, gonadal, and thyroid. It is not clear if any one system plays a primary role in the expression of the disease. Rather, it is likely that the net effect involves the synergistic and antagonistic effects of multiple hormones. Taken together, adrenal and gondadal steroid hormone deficiency, plus elevated PRL levels, probably greatly affect immune function in SS patients. - PublicationNP-completeness results and efficient approximations for radiocoloring in planar graphs(1/1/2000)
;Fotakis, Dimitris A. ;Nikoletseas., Sotiris E.; ;Spirakis, Paul G.Fotakis, Dimitris A.The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. The Radiocoloring (RC) of a graph G(V, E) is an assignment function ф: V — IN such that |ф(u) — ф (v)|≥ 2, when u,v are neighbors in G, and |ф(u) — ф (v)|≥ 1 when the minimum distance of u,v in G is two. The discrete number and the range of frequencies used are called order and span, respectively. The optimization versions of the Radiocoloring Problem (RCP) are to minimize the span or the order. In this paper we prove that the min span RCP is NP-complete for planar graphs. Next, we provide an O(nΔ) time algorithm (|V| = n) which obtains a radioco-loring of a planar graph G that approximates the minimum order within a ratio which tends to 2 (where 4Δ the maximum degree of G). Finally, we provide a fully polynomial randomized approximation scheme (fpras) for the number of valid radiocolorings of a planar graph G with λ colors, in the case X > 4Δ + 50. - PublicationMID-FIR properties of ELAIS sources(1/1/2001)
;Márquez, I. ;Masegosa, J. ;Morel, Thierry; ;Verma, Aprajita ;Väisänen, Petri H. ;Alexander, David M. ;Héraudeau, Ph ;Surace, Christian ;Pérez-Fournón, Ismaël ;Cabrera-Guerra, F. ;González-Serrano, José Ignacio ;González-Solares, Eduardo A. ;Serjeant, Stephen B.G. ;Oliver, Sebastian JamesRowan-Robinson, MichaelWe present the properties of all the galaxies detected by ISO at 7, 15 and 90μm in ELAIS northern fields. The spectral energy distribution (SED) of those 20 galaxies with IRAS detections can generally be well fitted by a predominant cirrus component plus a modest starburst contribution. Follow-up spectroscopy has shown that all the objects are emission-line galaxies but without a very intense star formation event. Most of the galaxies analyzed by means of optical R band photometry result to host an important exponential disk component, in good agreement with the SED IR modelling. We note that galaxies with morphological signs of perturbations seem to show slightly higher f15/f6.7 ratios, indicating that star formation could be more important in them. One of the objects is a broad-line, radio-quiet quasar at z=1.099; its spectral energy distribution indicates that it is a hyperluminous infrared galaxy (HLIG), the first HLIG detected in the ELAIS areas. - PublicationSpectroscopic properties of new IR galaxies detected in the european large area ISO survey(1/1/2001)
;Cabrera-Guerra, F. ;Pérez-Fournón, Ismaël ;González-Solares, Eduardo A. ;Fadda, Dario T. ;González-Serrano, José Ignacio ;Rowan-Robinson, Michael ;Serjeant, Stephen B.G. ;Verma, Aprajita ;Farrah, Duncan G.; ;Morel, Thierry ;Surace, Christian ;Oliver, Sebastian James ;Ciliegi, Paolo ;Pozzi, Francesca ;Lari, Carlo ;McMahon, R. G. ;Willott, Chris J. ;Vila-Vilaró, Baltasar ;Mature, I. ;La Franca, Fabio ;Héraudeau, Ph ;Masegosa, J. ;Márquez, I. ;Gruppioni, Carlotta ;Franceschini, AlbertoFlores, HectorWe present preliminary results of multi-object spectroscopy of new mid-, and far-infrared selected galaxies detected in the European Large Area ISO Survey (ELAIS). The data have been obtained with the fibre spectrographs WYFFOS at the William Herschel Telescope (Observatorio del Roque de los Muchachos, ORM, Canary Islands) and Hydra at the WIYN Telescope (Kitt Peak Observatory, Arizona). The sample includes ISO sources detected at 7, 15 and 90 μm and radio sources from our deep VLA survey in the ELAIS areas. - PublicationThe ISOPHOT 170 micron serendipity sky survey: A plea to FIRST(1/1/2001)
;Stickel, Manfred ;Lemke, Dietrich ;Klaas, Ulrich ;Beichman, Charles A. ;Rowan-Robinson, Michael; ;Bogun, Stefan ;Kessler, Martin F. ;Richter, Gotthard M.Stickel, ManfredThe ISOPHOT Serendipity Survey utilized the slew time between ISO's pointed observations with strip scanning measurements of the sky in the far-infrared (FIR) at 170μm. The integral 170μm fluxes for compact sources derived from the slews are put on an absolute flux level by using a number of galaxies as calibrator sources observed with ISOPHOT's photometric mapping mode, supplemented by Serendipity Survey observations of two planets and two asteroids with available model fluxes. A first group of 115 well-observed sources with a high signal-to-noise ratio in all four detector pixels having a galaxy association were extracted from the slew data with low (I100μm ≤ 15 MJy/sr) cirrus background. For all but a few galaxies, the 170μm fluxes are determined for the first time, which represents a significant increase in the number of galaxies with measured FIR fluxes beyond the IRAS 100μm limit. The large fraction of sources with a high F170μm/F100μm flux ratio indicates that a very cold (T < 20 K) dust component is present in many galaxies. The typical mass of the coldest dust component is MDust = 107.5 ± 0.5 M⊙, a factor 2 - 10 larger than that derived from IRAS fluxes alone. As a consequence, the gas-to-dust ratios are much closer to the canonical value for the Milky Way. A similar Serendipity Survey with FIRST has the prospects of delivering FIR data with a much higher angular resolution (PACS) or at longer wavelengths (SPIRE) than ISOPHOT, thereby providing either crucial information for the identification of compact sources in confused regions or extending the spectral coverage for a large number of sources and finding rare classes of very cold FIR emitters. - PublicationOn the average parallelism in trace monoids(1/1/2002)
;Michos, Ioannis C. ;Mairesse, Jean ;Michos, Ioannis C.Michos, Ioannis C. - PublicationInvolvement of D2 dopaminergic receptors in the modulation of hepatic drug metabolizing enzymes(1/1/2002)
;Charkitis, P. ;Alarick, M. A. ;Johnson, Elizabeth O. ;Marselos, MariosKonstandi, Maria - PublicationOn radiocoloring hierarchically specified planar graphs: PSPACE-completeness and approximations(1/1/2002)
;Andreou, Maria I. ;Fotakis, Dimitris A. ;Nikoletseas., Sotiris E.; ;Spirakis, Paul G.Andreou, Maria I.Hierarchical specifications of graphs have been widely used in many important applications, such as VLSI design, parallel programming and software engineering. A well known hierarchical specification model, considered in this work, is that of Lengauer [9, 10] referred to as L-specifications. In this paper we discuss a restriction on the Lspecifications resulting to graphs which we call Well-Separated (WS). This class is characterized by a polynomial time (to the size of the specification of the graph) testable combinatorial property. In this work we study the Radiocoloring Problem (RCP) on WS Lspecified hierarchical planar graphs. The optimization version of RCP studied here, consists in assigning colors to the vertices of a graph, such that any two vertices of distance at most two get different colors. The objective here is to minimize the number of colors used. This problem is equivalent to the problem of vertex coloring the square of a graph G, G2, where G2 has the same vertex set as G and there is an edge between any two vertices of G2 if their distance in G is at most 2. We first show that RCP is PSPACE-complete for WS L-specified hierarchical planar graphs. Second, we present a polynomial time 3- approximation algorithm as well as a more efficient 4-approximation algorithm for RCP on graphs of this class. We note that, the best currently known approximation ratio for the RCP on ordinary (non-hierarchical) planar graphs of general degree is 2([6, 1]). Note also that the only known results on any kind of coloring problems have been shown for another special kind of hierarchical graphs (unit disk graphs) achieving a 6-approximation solution [13]. - PublicationRadiocolorings in periodic planar graphs: PSPACE-completeness and efficient approximations for the optimal range of frequencies(1/1/2002)
;Fotakis, Dimitris A. ;Nikoletseas., Sotiris E.; ;Spirakis, Paul G.Fotakis, Dimitris A.The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. The Radiocoloring (RC) of a graph G(V,E) is an assignment function Φ: V → IN such that |Φ(u) - Φ(ν)| ≥ 2, when u, ν are neighbors in G, and |Φ(u) - Φ(ν)| ≥ 1 when the distance of u, ν in G is two. The range of frequencies used is called span. Here, we consider the optimization version of the Radiocoloring Problem (RCP) of finding a radiocoloring assignment of minimum span, called min span RCP. In this paper, we deal with a variation of RCP: that of satisfying frequency assignment requests with some periodic behavior. In this case, the interference graph is an (infinite) periodic graph. Infinite periodic graphs model finite networks that accept periodic (in time, e.g. daily) requests for frequency assignment. Alternatively, they may model very large networks produced by the repetition of a small graph. A periodic graph G is defined by an infinite two-way sequence of repetitions of the same finite graph Gi(Vi,Ei). The edge set of G is derived by connecting the vertices of each iteration Gi to some of the vertices of the next iteration Gi+1, the same for all Gi. The model of periodic graphs considered here is similar to that of periodic graphs in Orlin [13], Marathe et al [10]. We focus on planar periodic graphs, because in many cases real networks are planar and also because of their independent mathematical interest. We give two basic results: -We prove that the min span RCP is PSPACE-complete for periodic planar graphs.-We provide an O(n(Δ(Gi) + σ)) time algorithm, (where |Vi| = n, Δ(Gi) is the maximum degree of the graph Gi and σ is the number of edges connecting each Gi to Gi+1), which obtains a radiocoloring of a periodic planar graph G that approximates the minimum span within a ratio which tends to 2 as Δ(Gi) + σ tends to infinity. - PublicationLearning object farms and learning design in science education(1/1/2005)
;Stav, John Birger ;Thorseth, Trond Morten; ;Tsalapatas, HarikliaStav, John BirgerA Learning Object (LO) is a collection of digital pieces representing a minimal, independent and standalone educational unit. By combining XML and MathML technologies, together with the computing power of server based Computer Algebra Systems (CAS), it is possible to design new web-based information services where teachers and learners in parallel on the fly might easily design, produce/reproduce, explore and terminate various classes of digital LOs. Such an approach offers through Web large-scale production and harvesting of classes of graphical LOs, i.e. Learning Object Farms (LOF), that are adapted and dedicated to various training and learning scenarios targeting mathematics, statistics and natural science education. LOF offer homogenous and easy to use mechanisms for interactive heterogeneous mathematical, statistical and natural science presentations to be displayed through digital blackboards or a PC that is interconnected to a projector. Standard mathematical and scientific notation is obtained in both static and dynamical text based XHTML presentations, and in graphical presentations exploring Scalable Vector Graphics (SVG). A LOF might easily be included into LCMS. - PublicationThe price of defense(1/1/2006)
;Mavronicolas, Marios ;Michael, Loizos; ;Philippou, Anna ;Spirakis, Paul G.Mavronicolas, MariosWe consider a strategic game with two classes of confronting randomized players on a graph G(V, E): v attackers, each choosing vertices and wishing to minimize the probability of being caught, and a defender, who chooses edges and gains the expected number of attackers it catches. The Price of Defense is the worst-case ratio, over all Nash equilibria, of the optimal gain of the defender over its gain at a Nash equilibrium. We provide a comprehensive collection of trade-offs between the Price of Defense and the computational efficiency of Nash equilibria. - Through reduction to a Two-Players, Constant-Sum Game, we prove that a Nash equilibrium can be computed in polynomial time. The reduction does not provide any apparent guarantees on the Price of Defense. - To obtain such, we analyze several structured Nash equilibria: In a Matching Nash equilibrium, the support of the defender is an Edge Cover. We prove that they can be computed in polynomial time, and they incur a Price of Defense of α(G), the Independence Number of G. In a Perfect Matching Nash equilibrium, the support of the defender is a Perfect Matching. We prove that they can be computed in polynomial time, and they incur a Price of Defense of |V|/2. In a Defender Uniform Nash equilibrium, the defender chooses uniformly each edge in its support. We prove that they incur a Price of Defense falling between those for Matching and Perfect Matching Nash Equilibria; however, it is NP-complete to decide their existence. In an Attacker Symmetric and Uniform Nash equilibrium, all attackers have a common support on which each uses a uniform distribution. We prove that they can be computed in polynomial time and incur a Price of Defense of either |V|/2 or α(G). - PublicationUsing a blended-learning approach to support parent education in math and science(1/1/2008)
; ;Mavrotheris, EfstathiosPaparistodemou, EfiAt a time when mathematics and science provide essential knowledge tools and the foundations for lifelong learning skills, cross-national studies of student achievement indicate lack of mathematical and scientific competence for a considerable proportion of the student population across Europe. Acknowledging the central role of parents in children's learning, the EU-funded project SMASH (Success in MAth and Science at Home) aims to raise the educational standards of European youth in mathematics and science by cultivating underlying home cultures as springboards for learning. The project consortium is currently developing, and will then pilot test and deliver an innovative intercultural parent-trainer training course and related resources for professionals involved in parent education initiatives. Through the adoption of a blended learning approach that combines elearning with physical meetings, the course will equip these professionals with current knowledge, techniques, and implementation tools for the provision of high-quality, culturally differentiated parent training in mathematics and science education. Individuals completing the course will be trained to offer programs designed to educate parents of elementary and middle school children (ages 6-15) in how to best support their child's mathematics and science learning at home using pedagogically sound strategies and technologies. Parents unable to attend parent-training sessions could still study independently using the project knowledge base, which will provide open access to all of the project's outputs and resources. This, in turn, will contribute towards improved parental participation in children's learning. Parents will be empowered to understand and implement reform, providing a home environment that enhances children's scientific development and prepares them to meet the challenges of the digital age.