Showing papers by "University of Patras published in 2002"

Recent approaches to global optimization problems through Particle Swarm Optimization

Abstract: This paper presents an overview of our most recent results concerning the Particle Swarm Optimization (PSO) method. Techniques for the alleviation of local minima, and for detecting multiple minimizers are described. Moreover, results on the ability of the PSO in tackling Multiobjective, Minimax, Integer Programming and e1 errors-in-variables problems, as well as problems in noisy and continuously changing environments, are reported. Finally, a Composite PSO, in which the heuristic parameters of PSO are controlled by a Differential Evolution algorithm during the optimization, is described, and results for many well-known and widely used test functions are given.

Synthesis and characterization of hydroxyapatite crystals: A review study on the analytical methods

Abstract: For the synthesis of hydroxyapatite crystals from aqueous solutions three preparation methods were employed. From the experimental processes and the characterization of the crystals it was concluded that aging and precipitation kinetics are critical for the purity of the product and its crystallographic characteristics. The authentication details are presented along with the results from infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy, transmission and scanning electron photographs, and chemical analysis. Analytical data for several calcium phosphates were collected from the literature, extensively reviewed, and the results were grouped and presented in tables to provide comparison with the data obtained here.

Fiber-Reinforced Polymer Composites for Construction—State-of-the-Art Review

Abstract: A concise state-of-the-art survey of fiber-reinforced polymer (also known as fiber-reinforced plastic) composites for construction applications in civil engineering is presented. The paper is organized into separate sections on structural shapes, bridge decks, internal reinforcements, externally bonded reinforcements, and standards and codes. Each section includes a historical review, the current state of the art, and future challenges.

Particle swarm optimization method in multiobjective problems

Abstract: This paper constitutes a first study of the Particle Swarm Optimization (PSO) method in Multiobjective Optimization (MO) problems. The ability of PSO to detect Pareto Optimal points and capture the shape of the Pareto Front is studied through experiments on well-known non-trivial test functions. The Weighted Aggregation technique with fixed or adaptive weights is considered. Furthermore, critical aspects of the VEGA approach for Multiobjective Optimization using Genetic Algorithms are adapted to the PSO framework in order to develop a multi-swarm PSO that can cope effectively with MO problems. Conclusions are derived and ideas for further research are proposed.

Comparison of Nutritional Deficiencies after Roux- en-Y Gastric Bypass and after Biliopancreatic Diversion with Roux-en-Y Gastric Bypass

Abstract: Background: Patients undergoing either Roux-en-Y gastric bypass (RYGBP) or biliopancreatic diversion (BPD) with RYGBP are at risk of developing metabolic sequelae secondary to malabsorption.We compared the differences in nutritional complications between these two bariatric operations. Methods: A retrospective analysis of a prospective database was done. From June 1994 to December 2001, 243 morbidly obese patients underwent various bariatric procedures at our institution. Of these patients, 79 (BMI 45.6 ± SD=4.9) who underwent RYGBP (gastric pouch 15 ± 5ml, biliopancreatic limb 60-80 cm, alimentary limb 80-100 cm and common limb the remainder of the small intestine), and 95 super obese (BMI 57.2 ± 6.1) who underwent a BPD (gastric pouch 15 ± 5ml, biliopancreatic limb 150-200 cm, common limb 100 cm and alimentary limb the remainder of the small intestine), were selected and studied for the incidence of micronutrient deficiencies and level of serum albumin at yearly intervals postoperatively. A variety of nutritional parameters including Hb, Fe, ferritin, folic acid, vitamin B12 and serum albumin were measured preoperatively and compared postoperatively at 1, 3, 6, 12, 18 and 24 months, and yearly thereafter. Results: Nutritional parameters were compared preoperatively and at similar periods postoperatively. No statistically significant (P <0.05) difference in the occurrence of deficiency was observed between the groups for any of the nutritional parameters studied, except for ferritin, which showed a significant difference at the 2-year follow-up (37.7% low ferritin levels after RYGBP vs. 15.2% after BPD, P =0.0294). All of these deficiencies were mild, without clinical symptomatology and were easily corrected with additional supplementation of the deficient micronutrient, with no need for hospitalization. Regarding serum albumin, there was only one patient with a level below 3 g/dl in the RYGBP group and two in the BPD group.These three patients were hospitalized and received total parenteral nutrition for 3 weeks, without further complications. Conclusion:There was no significant difference in the incidence of deficiency of the nutritional parameters studied, except for ferritin, following RYGBP vs. BPD with RYGBP.The most common deficiencies encountered were of iron and vitamin B12. The incidence of hypoalbuminemia was negligible in both groups, with mean values above 4 g/dl.

Control of DNA replication licensing in a cell cycle

Abstract: To maintain genome integrity in eukaryotes, DNA must be duplicated precisely once before cell division occurs. A process called replication licensing ensures that chromosomes are replicated only once per cell cycle. Its control has been uncovered by the discovery of the CDKs (cyclin dependent kinases) as master regulators of the cell cycle and the initiator proteins of DNA replication, such as the Origin Recognition Complex (ORC), Cdc6/18, Cdt1 and the MCM complex. At the end of mitosis, the MCM complex is loaded on to chromatin with the aid of ORC, Cdc6/18 and Cdt1, and chromatin becomes licensed for replication. CDKs, together with the Cdc7 kinase, trigger the initiation of replication, recruiting the DNA replicating enzymes on sites of replication. The activated MCM complex appears to play a key role in the DNA unwinding step, acting as a replicating helicase and moves along with the replication fork, at the same time bringing the origins to the unlicensed state. The cycling of CDK activity in the cell cycle separates the two states of replication origins, the licensed state in G1-phase and the unlicensed state for the rest of the cell cycle. Only when CDK drops at the completion of mitosis, is the restriction on licensing relieved and a new round of replication is allowed. Such a CDK-regulated licensing control is conserved from yeast to higher eukaryotes, and ensures that DNA replication takes place only once in a cycle. Xenopus laevis and mammalian cells have an additional system to control licensing. Geminin, whose degradation at the end of mitosis is essential for a new round of licensing, has been shown to bind Cdt1 and negatively regulate it, providing a new insight into the regulation of DNA replication in higher eukaryotes.

Consumers’ willingness to pay for origin labelled wine: A Greek case study

Abstract: Quality agricultural products are assuming an increasingly important role in European Union (EU) agricultural and food policies. The potential for differentiating quality products and services on a regional basis has been recognised and legislation has been introduced for protecting the geographical indications and designations of origin for agricultural products and quality foodstuffs. Today, marketing strategies for quality products attempt to explore these new opportunities, trying to build on the products’ reputation and the image of their region of origin. This study employs a dichotomous choice model to identify the socio‐economic characteristics that influence Greek consumers’ willingness to pay for an origin labelled wine. The results indicate that wine consumers’ willingness to pay varies only according to social and demographic characteristics. Furthermore, the mean willingness to pay was estimated using two alternative econometric specifications of the dichotomous choice model. We have found that non‐quality wine consumers are willing to pay double the price of a bottle of normal table wine if the alternative provides for a guarantee of the place of origin of the wine. Their decision is found to be dependent only upon education and affiliation with the place of origin. The model specifications are compared and useful conclusions referring to price policy for origin labelled wines and their marketing are drawn.

Identification of coupling direction: application to cardiorespiratory interaction.

Abstract: We consider the problem of experimental detection of directionality of weak coupling between two self-sustained oscillators from bivariate data. We further develop the method introduced by Rosenblum and Pikovsky [Phys. Rev. E 64, 045202 (2001)], suggesting an alternative approach. Next, we consider another framework for identification of directionality, based on the idea of mutual predictability. Our algorithms provide directionality index that shows whether the coupling between the oscillators is unidirectional or bidirectional, and quantifies the asymmetry of bidirectional coupling. We demonstrate the efficiency of three different algorithms in determination of directionality index from short and noisy data. These techniques are then applied to analysis of cardiorespiratory interaction in healthy infants. The results reveal that the direction of coupling between cardiovascular and respiratory systems varies with the age within the first 6 months of life. We find a tendency to change from nearly symmetric bidirectional interaction to nearly unidirectional one (from respiration to the cardiovascular system).

Strength prediction of bolted joints in graphite/epoxy composite laminates

Abstract: A parametric finite element analysis was conducted to investigate the effect of failure criteria and material property degradation rules on the tensile behaviour and strength of bolted joints in graphite/epoxy composite laminates. The analysis was based on a three-dimensional progressive damage model (PDM) developed earlier by the authors. The PDM comprises the components of stress analysis, failure analysis and material property degradation. The predicted load–displacement curves and failure loads of a single-lap single-bolt joint were compared with experimental data for different joint geometries and laminate stacking sequences. The stiffness of the joint was predicted with satisfactory accuracy for all configurations. The predicted failure load was significantly influenced by the combination of failure criteria and degradation rules used. A combination of failure criteria and material property degradation rules that leads to accurate strength prediction is proposed. For all the analyses performed, the macroscopic failure mechanism of the joint and the damage progression were also predicted.

A Novel Monte Carlo Scheme for the Rapid Equilibration of Atomistic Model Polymer Systems of Precisely Defined Molecular Architecture

Abstract: Two novel connectivity-altering atomistic Monte Carlo moves are presented for the fast equilibration of condensed phases of long-chain systems with a variety of chain architectures. With the new moves, isotropic or oriented melts of linear or long-chain branched polymers, dense brushes of terminally grafted macromolecules, and cyclic peptides can be simulated. Results concerning the structural, conformational, and volumetric properties of linear, monodisperse polyethylene melts, simulated with a new united-atom molecular model, are in excellent agreement with experimental data.

Regional and Cellular Mapping of cAMP Response Element-Mediated Transcription during Naltrexone-Precipitated Morphine Withdrawal

Abstract: Chronic opiate exposure is associated with upregulation of the cAMP signaling pathway and the transcription factor cAMP response element-binding protein in the locus ceruleus (LC) and certain other brain areas. To determine whether these adaptations ultimately affect transcription mediated by the cAMP response element (CRE), we induced morphine dependence in CRE-LacZ transgenic mice and performed a regional and cellular mapping of beta-galactosidase (beta-gal) expression during naltrexone-precipitated withdrawal. Consistent with our model of opiate dependence, beta-gal expression increased in the LC, but decreased in the lateral ventral tegmental area (VTA) and dorsal raphe nucleus (DRN). In addition, withdrawal increased beta-gal expression in the continuum of the extended amygdala and nucleus accumbens, macrostructures associated with the coupling of emotional stimuli to motor and autonomic responses. At the cellular level, in the central nucleus of the amygdala, beta-gal was found in cells both with and without mu opioid receptors as well as in corticotropin-releasing factor-expressing cells. In nucleus accumbens, beta-gal was expressed in several major subpopulations of neurons. In LC, beta-gal expression was induced predominantly in tyrosine hydroxylase-expressing cells, whereas in the VTA and DRN the majority of cells expressing beta-gal were nonmonoaminergic. These results show that molecular adaptations to chronic morphine alter CRE-mediated transcription during opiate withdrawal in physiologically salient regions involved in arousal, reward, mood, and affective responses. We propose that CRE-mediated transcription serves as a functional marker for neuronal plasticity during withdrawal. CRE-mediated transcription may itself contribute to re-establishing homeostasis in the organism through target gene regulation in these regions.

A High-Performance Solid-State Dye-Sensitized Photoelectrochemical Cell Employing a Nanocomposite Gel Electrolyte Made by the Sol–Gel Route

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Distribution of Human Virus Contamination in Shellfish from Different Growing Areas in Greece, Spain, Sweden, and the United Kingdom

Abstract: Viral pollution in shellfish has been analyzed simultaneously across a wide range of geographical regions, with emphasis on the concomitant variations in physicochemical characteristics and social features. The methods for sample treatment and for the detection of human enteric viruses were optimized by the participating laboratories. The second part of this study involves the selection of a protocol for virus detection, which was validated by analyzing the distribution and concentration of human viral pathogens under diverse conditions during an 18-month period in four European countries. Shellfish-growing areas from diverse countries in the north and south of Europe were defined and studied, and the microbiological quality of the shellfish was analyzed. Human adenovirus, Norwalk-like virus, and enterovirus were identified as contaminants of shellfish in all the participating countries. Hepatitis A virus was also isolated in all areas except Sweden. The seasonal distribution of viral contamination was also described. Norwalk-like virus appeared to be the only group of viruses that demonstrated seasonal variation, with lower concentrations occurring during warm months. The depuration treatments currently applied were shown to be adequate for reducing Escherichia coli levels but ineffective for the elimination of viral particles. The human adenoviruses detected by PCR correlate with the presence of other human viruses and could be useful as a molecular index of viral contamination in shellfish.

Analysis and design of an inverted-F antenna printed on a PCMCIA card for the 2.4 GHz ISM band

Abstract: The development of small integrated antennas plays a significant role in the progress of rapidly expanding commercial communication applications. This paper addresses the analysis and design of an inverted-F antenna (IFA) printed on a PCMCIA card. The antenna is compact, easy to manufacture, and efficient, with an omni-directional pattern and a bandwidth of 250 MHz. The performance of the integrated IFA/PCMCIA system was simulated using two commercial method of moments codes, and validated with measurements on a fabricated prototype.

Transcription factor E2F-1 acts as a growth-promoting factor and is associated with adverse prognosis in non-small cell lung carcinomas.

Abstract: Numerous upstream stimulatory and inhibitory signals converge to the pRb/E2F pathway, which governs cell-cycle progression, but the information concerning alterations of E2F-1 in primary malignancies is very limited. Several in vitro studies report that E2F-1 can act either as an oncoprotein or as a tumour suppressor protein. In view of this dichotomy in its functions and its critical role in cell cycle control, this study examined the following four aspects of E2F-1 in a panel of 87 non-small cell lung carcinomas (NSCLCs), previously analysed for defects in the pRb-p53-MDM2 network: firstly, the status of E2F-1 at the protein, mRNA and DNA levels; secondly, its relationship with the kinetic parameters and genomic instability of the tumours; thirdly, its association with the status of its transcriptional co-activator CBP, downstream target PCNA and main cell cycle regulatory and E2F-1-interacting molecules pRb, p53 and MDM2; and fourthly, its impact on clinical outcome. The protein levels of E2F-1 and its co-activator CBP were significantly higher in the tumour area than in the corresponding normal epithelium (p Asp) and one carrying a polymorphism at codon 393 (Gly-->Ser). Carcinomas with increased E2F-1 positivity demonstrated a significant increase in their growth indexes (r=0.402, p=0.001) and were associated with adverse prognosis (p=0.033 by Cox regression analysis). The main determinant of the positive association with growth was the parallel increase between E2F-1 staining and proliferation (r=0.746, p<0.001), whereas apoptosis was not influenced by the status of E2F-1. Moreover, correlation with the status of the pRb-p53-MDM2 network showed that the cases with aberrant pRb expression displayed significantly higher E2F-1 indexes (p=0.033), while a similar association was noticed in the group of carcinomas with deregulation of the p53-MDM2 feedback loop. In conclusion, the results suggest that E2F-1 overexpression may contribute to the development of NSCLCs by promoting proliferation and provide evidence that this role is further enhanced in a genetic background with deregulated pRb-p53-MDM2 circuitry.

Families of Polynuclear Manganese, Cobalt, Nickel and Copper Complexes Stabilized by Various Forms of Di-2-pyridyl Ketone

Abstract: The synthetic and structural chemistry of polynuclear manganese, cobalt, nickel and copper carboxylate complexes, stabilized by various forms of di-2-pyridyl ketone, is discussed. The structural diversity displayed by the described complexes stems from the ability of the doubly and singly deprotonated forms of the gem-diol form of di-2-pyridyl ketone, or the monoanion of the hemiacetal form of this ligand, to adopt a variety of coordination modes. The nuclearities of the clusters vary from four to fourteen. Perhaps the most aesthetically pleasing families are the "flywheel Cu 12 clusters, and the Co 9 and Ni 9 complexes in which the nine metal ions adopt a topology of two square pyramids sharing a common apex. A means of increasing the ground-state total spin value of a polynuclear 3d-metal cluster is also proposed. The approach is based on the replacement of hydroxo bridges, that most often propagate antiferromagnetic exchange interactions in clusters, by the end-on azido ligand, which is a well known fe...

The role of Seprafilm bioresorbable membrane in the prevention and therapy of endometrial synechiae.

Abstract: This randomized controlled blind prospective study is undertaken to evaluate the safety and efficacy of Seprafilm--a novel bioresorbable membrane of chemically modified hyaluronic acid and carboxymethylcellulose--in prevention and reduction of postoperative endometrial and endocervical synechiae formation after general suction evacuation or curettage for incomplete, missed, and recurrent abortion. In total, 150 patients with incomplete or missed abortion participated in the clinical study. The study population was divided into two main groups. In the treatment (Seprafilm) group (n=50), application of Seprafilm membrane in the endometrial cavity and the cervical canal was used after the suction evacuation and/or the curettage. In the control group (n=100), nothing was inserted in the uterus. Both groups were divided into two subgroups: patients who had no previous suction or curettage, (with no previous DC in the controls, pregnancy occurred only in 54%. It was also demonstrated with hysterosalpingography (HSG) that patients with one or more previous interventions and no pregnancy 8 months later were adhesion free in 90% of the patients where Seprafilm was used, and only 50% in the untreated group. The membrane was tested on the endometrial area of the uterus and did not produce any adverse reaction. Ultrasound controls did not show any abnormal echoes. Intrauterine insertion of Seprafilm is safe, prevents the appearance of endocervical adhesions or endometrial synechiae after curettage, and reduces the area of the endometrial cavity occupied by them in a large percent of cases. It also seems that its use improves the possibility of a new pregnancy and fertility.

Orbital dynamics of three-dimensional bars — III. Boxy/peanut edge-on profiles

Abstract: We present families, and sets of families, of periodic orbits that provide building blocks for boxy and peanut (hereafter b/p) edge-on profiles. We find cases where the b/p profile is confined to the central parts of the model and cases where a major fraction of the bar participates in this morphology. A b/p feature can be built either by 3D families associated with 3D bifurcations of the x1 family, or, in some models, even by families related with the z-axis orbits and existing over large energy intervals. The ‘X’ feature observed inside the boxy bulges of several edgeon galaxies can be attributed to the peaks of successive x1v1 orbits, provided their stability allows it. However in general, the x1v1 family has to overcome the obstacle of a S → � → S transition in order to support the structure of a b/p feature. Other families that can be the backbones of b/p features are x1v4 and z3.1s. The morphology and the size of the boxy or peanut-shaped structures we find in our models are determined by the presence and stability of the families that support b/p features. The present study favours the idea that the observed edge-on profiles are the imprints of families of periodic orbits that can be found in appropriately chosen Hamiltonian systems, describing the potential of the bar.

A solvent-free composite polymer/inorganic oxide electrolyte for high efficiency solid-state dye-sensitized solar cells

Abstract: A new solvent-free composite polymer electrolyte consisting of high-molecular mass polyethylene oxide (PEO) filled with titanium oxide and containing LiI and I2 was developed. The introduction of the inorganic filler (TiO2 Degussa P25) into the polymer matrix produces dramatic morphological changes to the host polymer structure. Upon addition of the inorganic oxide, the surface roughness increases, with respect to the original polymer and in parallel, the fractal dimension decreases. Both the thermograms and the atomic force microscope (AFM) pictures confirm the amorphicity of the composite electrolyte. The polymer sub-units are held together in a parallel orientation, forming straight long chains of about 500 nm in width, along which TiO2 spherical particles of about 20–25 nm in diameter are distributed. The polymer chains separated by the titania particles are arranged in a three-dimensional, mechanically stable network, that creates free space and voids into which the iodide/triodide anions can easily migrate. All solid-state dye-sensitized solar cells fabricated using this composite electrolyte present high efficiencies (typical maximum incident photon to current efficiency (IPCE) as high as 40% at 520 nm and overall conversion efficiency (η) of 0.96% (Voc=0.67 V, Jsc=2.050 mA/cm2, FF=39%)) under direct solar irradiation. Further improvement of the photovoltaic performance is expected by optimization of the electrolyte parameters and of the cell assembly.

Electromagnetically induced transparency and controlled group velocity in a multilevel system

Abstract: We analyze the interaction of N laser fields with a $(N+1)$-level quantum system. A general analytic expression for the steady-state linear susceptibility for a probe-laser field is obtained and we show that the system can exhibit multiple electromagnetically induced transparency, with at most $N\ensuremath{-}1$ transparency windows occurring in the system. The group velocity of the probe-laser pulse can also be controlled.

The Probabilistic Analysis of a Greedy Satisfiability Algorithm

Abstract: Consider the following simple, greedy Davis-Putnam algorithm applied to a random 3-CNF formula of constant density c: Arbitrarily set to TRUE a literal that appears in as many clauses as possible, irrespective of their size (and irrespective of the number of occurrences of the negation of the literal). Reduce the formula. If any unit clauses appear, then satisfy their literals arbitrarily, reducing the formula accordingly, until no unit clause remains. Repeat. We prove that for c < 3.42 a slight modification of this algorithm computes a satisfying truth assignment with probability asymptotically bounded away from zero. Previously, algorithms of increasing sophistication were shown to succeed for c < 3.26. Preliminary experiments we performed suggest that c ? 3.6 is feasible running algorithms like the above, which take into account not only the number of occurrences of a literal but also the number of occurrences of its negation, irrespectively of clause-size information.