University of Patras

About: University of Patras is a education organization based out in Pátrai, Greece. It is known for research contribution in the topics: Population & Catalysis. The organization has 13372 authors who have published 31263 publications receiving 677159 citations. The organization is also known as: Panepistímio Patrón.

Analysis of the rocking response of rigid blocks standing free on a seismically isolated base

Abstract: SUMMARY This paper examines the rocking response and stability of rigid blocks standing free on an isolated base supported: (a) on linear viscoelastic bearings, (b) on single concave and (c) on double concave spherical sliding bearings. The investigation concludes that seismic isolation is beneficial to improve the stability only of small blocks. This happens because while seismic isolation increase the ‘static’ value of the minimum overturning acceleration, this value remains nearly constant as we move to larger blocks or higher frequency pulses; therefore, seismic isolation removes appreciably from the dynamics of rocking blocks the beneficial property of increasing stability as their size increases or as the excitation pulse period decreases. This remarkable result suggests that free- standing ancient classical columns exhibit superior stability as they are built (standing free on a rigid foundation) rather than if they were seismically isolated even with isolation system with long isolation periods. The study further confirms this finding by examining the seismic response of the columns from the peristyle of two ancient Greek temples when subjected to historic records. Copyright © 2011 John Wiley & Sons, Ltd.

Dynamic bandwidth allocation in flexible OFDM-based networks

Abstract: We propose a general policy to allocate subcarriers to time-varying traffic in a flexible OFDM optical network. We compare the OFDM network performance to that of a fixed-grid WDM network using simulations.

Complications and risk factors related to the extent of surgery in thyroidectomy. Results from 2,043 procedures.

Abstract: OBJECTIVE: To evaluate the rate of complications and the risk factors in relation to the extent of surgery in patients undergoing thyroidectomy in a tertiary university center. DESIGN: Data were collected retrospectively from 2,043 consecutive patients who underwent thyroid surgery for various thyroid diseases at the University Hospital of Patras, Greece, between January 1996 and December 2007. recurrent laryngeal nerve palsy (rLNP) and hypoparathyroidism were set as the primary end points, while hematoma and wound infection were set as the secondary endpoints. rESULTS: Total, near-total and subtotal thyroidectomy was performed in 1,149, 777 and 117 patients, respectively. Transient rLNP occurred in 34 (1.6%) and permanent in 19 (0.9%) patients. Multivariate logistic regression analysis showed that extended resection (Or-odds ratio-1.6), Graves’ disease (Or 2.7), thyroiditis (Or 2.1), recurrent goiter (Or 2.3) and thyroid malignancy (Or 1.7) were all independent risk factors for transient rLNP, whereas Graves’ disease (Or 2.2) and recurrent goiter (Or 1.7) emerged as independent risk factors for permanent rLNP. The rates of transient and permanent hypoparathyroidism were 27.8% and 4.8%, respectively. Multivariate analysis for transient hypoparathyroidism revealed that the extent of surgical resection (Or 2.2), Graves’ disease (Or 2.1), recurrent goiter (Or 1.7), female gender (Or 1.5) and specimen weight (Or 1.6) were independent predictors. However, the extent of surgical resection (Or 2.7), Graves’ disease (Or 1.8), recurrent goiter (Or 1.5) and malignant disease (Or 1.5) were independent risk factors for permanent hypoparathy roidism. Postoperative wound infection and hematoma occurred in 6 (0.3%) and 27 (1.3%) patients, respectively. No correlation was observed between wound infection or postoperative hemorrhage and the extent of surgery. CONCLUSIONS: Despite the higher morbidity, total thyroidectomy is emerging as an attractive surgical option even for benign thyroid disease due to the risk of subclinical (occult) malignancy, the possibility of goiter relapse as well as of the increased risk of complications following reoperation.