Showing papers by "University of Patras published in 2004"
TL;DR: In this article, the authors reviewed existing knowledge with regard to organic aerosol (OA) of importance for global climate modelling and defined critical gaps needed to reduce the involved uncertainties, and synthesized the information to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosols.
Abstract: The present paper reviews existing knowledge with regard to Organic Aerosol (OA) of importance for global climate modelling and defines critical gaps needed to reduce the involved uncertainties. All pieces required for the representation of OA in a global climate model are sketched out with special attention to Secondary Organic Aerosol (SOA): The emission estimates of primary carbonaceous particles and SOA precursor gases are summarized. The up-to-date understanding of the chemical formation and transformation of condensable organic material is outlined. Knowledge on the hygroscopicity of OA and measurements of optical properties of the organic aerosol constituents are summarized. The mechanisms of interactions of OA with clouds and dry and wet removal processes parameterisations in global models are outlined. This information is synthesized to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosol. The sources of uncertainties at each step of this process are highlighted as areas that require further studies.
2,863 citations
TL;DR: The theories that are reviewed are the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the thermodynamic approach and the extended DLVO theory, which provide the basis for theoretical analysis of the receptor-ligand interactions.
Abstract: This article reviews the mechanisms of bacterial adhesion to biomaterial surfaces, the factors affecting the adhesion, the techniques used in estimating bacteria-material interactions and the models that have been developed in order to predict adhesion. The process of bacterial adhesion includes an initial physicochemical interaction phase and a late molecular and cellular one. It is a complicated process influenced by many factors, including the bacterial properties, the material surface characteristics, the environmental factors, such as the presence of serum proteins and the associated flow conditions. Two categories of techniques used in estimating bacteria-material interactions are described: those that utilize fluid flowing against the adhered bacteria and counting the percentage of bacteria that detach, and those that manipulate single bacteria in various configurations which lend themselves to more specific force application and provide the basis for theoretical analysis of the receptor-ligand interactions. The theories that are reviewed are the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the thermodynamic approach and the extended DLVO theory. Over the years, significant work has been done to investigate the process of bacterial adhesion to biomaterial surfaces, however a lot of questions still remain unanswered.
1,086 citations
TL;DR: This process has great potential for low-cost H2 generation in fuel cells for small portable applications where liquid fuel storage is essential and where systems must be small, simple, and robust.
Abstract: Ethanol and ethanol-water mixtures were converted directly into H2 with approximately 100% selectivity and >95% conversion by catalytic partial oxidation, with a residence time on rhodium-ceria catalysts of <10 milliseconds. Rapid vaporization and mixing with air with an automotive fuel injector were performed at temperatures sufficiently low and times sufficiently fast that homogeneous reactions producing carbon, acetaldehyde, ethylene, and total combustion products can be minimized. This process has great potential for low-cost H2 generation in fuel cells for small portable applications where liquid fuel storage is essential and where systems must be small, simple, and robust.
933 citations
TL;DR: The approaches include transformations of the objective function through the recently proposed deflection and stretching techniques, as well as a repulsion source at each detected minimizer, resulting in an efficient algorithm which has the ability to avoid previously detected solutions and, thus, detect all global minimizers of a function.
Abstract: This paper presents approaches for effectively computing all global minimizers of an objective function. The approaches include transformations of the objective function through the recently proposed deflection and stretching techniques, as well as a repulsion source at each detected minimizer. The aforementioned techniques are incorporated in the context of the particle swarm optimization (PSO) method, resulting in an efficient algorithm which has the ability to avoid previously detected solutions and, thus, detect all global minimizers of a function. Experimental results on benchmark problems originating from the fields of global optimization, dynamical systems, and game theory, are reported, and conclusions are derived.
718 citations
TL;DR: In this article, the photocatalytic degradation of a model azo-dye (Acid Orange, AO7) in aerated aqueous TiO2 dispersion has been studied under visible light (λ>400 nm) irradiation.
Abstract: The photocatalytic degradation of a model azo-dye (Acid Orange, AO7) in aerated aqueous TiO2 dispersion has been studied under visible light (λ>400 nm) irradiation. The presence and role of oxidative species, such as singlet oxygen ( 1 O 2 ), superoxide (O2− ) and hydroperoxy (HO2 ) radicals was examined with the use of appropriate quenchers of these species. The reaction pathway of dye degradation was also investigated by monitoring the temporal evolution of intermediates and final products on both the photocatalyst surface and in solution, with the use of a variety of techniques, including GC–MS, FTIR and UV-Vis spectroscopies. It has been found that complete decolorization of the solution may be achieved, accompanied by a substantial decrease of the chemical oxygen demand (COD) of the solution. Evidence is presented that the main oxidative species is O2− (or HO2 ), while singlet oxygen, when formed, is also active. The adsorbed dye molecule is initially cleaved in the vicinity of the azo-bond and the resulting fragments are oxidized toward compounds of progressively lower molecular weight and, eventually, to CO2 and inorganic ions. However, when the solution is bleached, formation of active oxidative species does not take place, oxidation reactions cease and the concentrations of the dye intermediates remain practically stable upon further exposure to visible light irradiation. Formation of photoinduced hydrogen peroxide, which is also generated under the present conditions, also stops when the dye concentration in solution drops to very low levels. This behavior has been explained evoking the photosensitization mechanism of wide band-gap semiconductors, according to which the reaction is triggered by excitation of the dye molecule by visible light photons, followed by charge injection to the conduction band of the semiconductor and subsequent production of active oxygen radicals. Formation of the latter oxidizing species is possible only in the presence of visible light-absorbing compounds and cannot take place after fragmentation of the parent AO7 molecule in the vicinity of the azo-bond and decolorization.
596 citations
TL;DR: In this paper, various supports and immobilization techniques have been proposed and tested for application in wine making, cider-making, brewing, distillates, potable alcohol and novel beverages production.
579 citations
TL;DR: In this paper, the reaction of steam reforming of ethanol over nickel catalysts supported on γ -Al 2 O 3, La 2 O3, and La 2O 3 / γ-Al O 3 is investigated employing transient and steady-state techniques.
558 citations
TL;DR: The ability of the PLA-Peg and PLGA-PEG nanoparticles to evade rapid phagocytocis has extended the range of sites within the body that the nanoparticles can reach, which has significant implications with regard to their application in controlled drug delivery and targeting.
Abstract: The preparation, properties and potential applications in drug delivery of biocompatible and biodegradable PLA-PEG and PLGA-PEG nanoparticles are discussed. PLA-PEG and PLGA-PEG nanoparticles have been produced by emulsification-solvent evaporation, solvent displacement and salting out methods. The nanoparticles can be stored as freeze-dried powders, but an adequate amount of a suitable lyoprotectant should be added prior lyophilisation to prevent nanoparticle aggregation and retain nanoparticle redispersibility. The nanoparticles have a core-shell structure with a PLA core and a PEG coating. Their basic colloidal properties and degradation depend on copolymer composition. The PLA-PEG and PLGA-PEG nanoparticles exhibit prolonged blood circulation following intravenous administration to animals. The composition of the nanoparticles determine their biodistribution properties, probably through its effects on the effectiveness of the PEG steric barrier and the size of the nanoparticles. The ability of the PLA-PEG and PLGA-PEG nanoparticles to evade rapid phagocytocis has extended the range of sites within the body that the nanoparticles can reach, which has significant implications with regard to their application in controlled drug delivery and targeting. The PLA-PEG and PLGA-PEG nanoparticles can be loaded with a variety of bioactive agents achieving satisfactory loading, especially in the case of hydrophobic drugs. The nanoparticles have been investigated for the treatment of infectious diseases and cancer, the intravenous and mucosal delivery of proteins, and oligonucleotide and gene delivery. The results have been encouraging and PLA-PEG and PLGA-PEG nanoparticle formulations, improving the therapeutic potential of both established and new drugs, may be expected to be available in the near future.
441 citations
01 Jan 2004
TL;DR: A mathematical description ofFCM is presented and a new methodology based on fuzzy logic techniques for developing the FCM is examined, and the applicability of FCM to model the supervisor of complex systems is discussed.
Abstract: This research deals with the soft computing methodology of fuzzy cognitive map (FCM). Here a mathematical description of FCM is presented and a new methodology based on fuzzy logic techniques for developing the FCM is examined. The capability and usefulness of FCM in modeling complex systems and the application of FCM to modeling and describing the behavior of a heat exchanger system is presented. The applicability of FCM to model the supervisor of complex systems is discussed and the FCM-supervisor for evaluating the performance of a system is constructed; simulation results are presented and discussed.
395 citations
TL;DR: In this article, the authors obtained sharp constants for Sobolev inequalities for higher-order fractional derivatives on the sphere, and gave a new proof of a theorem of W. Beckner concerning conformally invariant higher order differential operators.
364 citations
TL;DR: This proposed learning procedure is a promising approach for exploiting experts' involvement with their subjective reasoning and at the same time improving the effectiveness of the FCM operation mode and thus it broadens the applicability of FCMs modeling for complex systems.
TL;DR: In this article, the authors provide an integrated view of rural entrepreneurship and set the agenda for future research in the area, where rural entrepreneurship is depicted as a three-stage sequential process highly influenced by specific territorial characteristics.
Abstract: The present work provides an integrated view of rural entrepreneurship and sets the agenda for future research in the area. Rurality defines a territorially specific entrepreneurial milieu with distinct physical, social and economic characteristics. Location, natural resources and the landscape, social capital, rural governance, business and social networks, as well as information and communication technologies, exert dynamic and complex influences on entrepreneurial activity in rural areas. Rurality is viewed as a dynamic entrepreneurial resource that shapes both opportunities and constraints. Rural entrepreneurship is depicted as a three‐stage sequential process highly influenced by specific territorial characteristics. The proposed research agenda addresses issues related to theoretical studies concerning entrepreneurial processes in rural areas and more applied issues concerning the formulation of integrated and competent policies supporting entrepreneurship in such areas.
TL;DR: In this article, the authors investigated the effects of the terrorist attacks of September 11, 2001 on a set of airline stocks listed at various international stock markets, using the Market Model as the relevant return generating mechanism.
TL;DR: In this paper, the catalytic activity of M/TiO2 catalysts (M=Pt, Rh, Ru, Pd) for the water-gas shift (WGS) reaction has been investigated in the temperature range of 150-450°C with respect to the structural and morphological properties of the dispersed metallic phase and the support.
19 Jun 2004
TL;DR: Experimental results indicate that the extent of information exchange among subpopulations assigned to different processor nodes, bears a significant impact on the performance of the algorithm.
Abstract: Parallel processing has emerged as a key enabling technology in modern computing. Recent software advances have allowed collections of heterogeneous computers to be used as a concurrent computational resource. In this work we explore how differential evolution can be parallelized, using a ring-network topology, so as to improve both the speed and the performance of the method. Experimental results indicate that the extent of information exchange among subpopulations assigned to different processor nodes, bears a significant impact on the performance of the algorithm. Furthermore, not all the mutation strategies of the differential evolution algorithm are equally sensitive to the value of this parameter.
TL;DR: The dynamic response of an initially spherical capsule subject to different externally imposed flows is examined in this article, where two constitutive laws are used for the description of the membrane mechanics, assuming negligible bending resistance.
Abstract: The dynamic response of an initially spherical capsule subject to different externally imposed flows is examined. The neo-Hookean and Skalak et al. (Biophys. J., vol. 13 (1973), pp. 245–264) constitutive laws are used for the description of the membrane mechanics, assuming negligible bending resistance. The viscosity ratio between the interior and exterior fluids of the capsule is taken to be unity and creeping-flow conditions are assumed to prevail. The capillary number , beyond the interval of stability, the membrane has two tips along the direction of elongation where the deformation is most severe, and no equilibrium shapes could be identified. For both regions outside the interval of stability, the membrane model is not appropriate and bending resistance is essential to obtain realistic capsule shapes. This pattern persists for the two constitutive laws that were used, with the Skalak et al. law producing a wider stability interval than the neo-Hookean law owing to its strain hardening nature.
TL;DR: A novel 0–1 integer programming formulation of the university timetabling problem is presented and it is shown that this model is solvable by existing software tools with IP solvers, even for large departments.
TL;DR: Findings show a clear type-1 cytokine polarization of the autoimmune response in adult ITP that persists irrespective of disease status.
TL;DR: Experimental results highlight the effectiveness of the proposed topology under wide load changes, establishing it as an appropriate solution in order to develop flyback converters, even at the power range of 500 W.
Abstract: Active clamp topologies of low power dissipation have become a very attractive solution in order to limit overvoltages in flyback converters. Although many suitable topologies have been introduced for the case of discontinuous conduction mode (DCM), where the duty cycle value depends on the load level, in continuous conduction mode (CCM) it is more difficult to appropriately design such topologies so as to "sense" load changes-due to the small duty cycle divergence under wide load variation. Taking for granted that in order to achieve high power-factor correction in these converters, CCM is a more attractive mode of operation, a drastic solution for this case that will manage to eliminate voltage stresses under wide load changes has become very essential. For this purpose, this paper presents an active clamp topology with small power dissipation, suitable for flyback converters operating in CCM mode. Its main idea is the use of a load-dependent current source, consisting of an auxiliary converter operating in DCM mode. Experimental results highlight the effectiveness of the proposed topology under wide load changes, establishing it as an appropriate solution in order to develop flyback converters, even at the power range of 500 W.
TL;DR: A 4-R-Mode factor model determined from the analysis showed its useful role in investigating hydrogeological parameters affecting NO(3)(-) concentration, such as its dilution by upcoming groundwater of the recharge areas.
TL;DR: The significant decrease in PSH, CSH and NPSSC, as well as the increase in PSSP, NPSSR, lipid peroxidation and protein oxidation levels after PTZ-induced seizure indicate increased oxidative damage in hippocampus, although the levels of GSH and GSSG do not change significantly.
TL;DR: In this paper, the authors used the smaller alignment index (SALI) to distinguish rapidly and with certainty between ordered and chaotic motion in Hamiltonian flows, based on the different behaviour of the SALI for the two cases: the index fluctuates around non-zero values for ordered orbits, while it tends rapidly to zero for chaotic orbits.
Abstract: We use the smaller alignment index (SALI) to distinguish rapidly and with certainty between ordered and chaotic motion in Hamiltonian flows This distinction is based on the different behaviour of the SALI for the two cases: the index fluctuates around non-zero values for ordered orbits, while it tends rapidly to zero for chaotic orbits We present a detailed study of SALI’s behaviour for chaotic orbits and show that in this case the SALI exponentially converges to zero, following a time rate depending on the difference of the two largest Lyapunov exponents σ1 ,σ 2 ie SALI ∝ e −(σ
TL;DR: Cerebral CT angiography has an equal sensitivity to DSA in the detection of intracranial aneurysms >3 mm, and the use of digital subtractionAngiography as a diagnostic tool can be limited in equivocal cases.
TL;DR: In this paper, the authors analyzed the expression of hCdt1, hCdc6, and hGeminin in a series of non-small-cell lung carcinomas, and investigated for putative relations with G1/S phase regulators, tumor kinetics, and ploidy.
Abstract: Replication licensing ensures once per cell cycle replication and is essential for genome stability. Overexpression of two key licensing factors, Cdc6 and Cdt1, leads to overreplication and chromosomal instability (CIN) in lower eukaryotes and recently in human cell lines. In this report, we analyzed hCdt1, hCdc6, and hGeminin, the hCdt1 inhibitor expression, in a series of non-small-cell lung carcinomas, and investigated for putative relations with G1/S phase regulators, tumor kinetics, and ploidy. This is the first study of these fundamental licensing elements in primary human lung carcinomas. We herein demonstrate elevated levels (more than fourfold) of hCdt1 and hCdc6 in 43% and 50% of neoplasms, respectively, whereas aberrant expression of hGeminin was observed in 49% of cases (underexpression, 12%; overexpression, 37%). hCdt1 expression positively correlated with hCdc6 and E2F-1 levels (P = 0.001 and P = 0.048, respectively). Supportive of the observed link between E2F-1 and hCdt1, we provide evidence that E2F-1 up-regulates the hCdt1 promoter in cultured mammalian cells. Interestingly, hGeminin overexpression was statistically related to increased hCdt1 levels (P = 0.025). Regarding the kinetic and ploidy status of hCdt1- and/or hCdc6-overexpressing tumors, p53-mutant cases exhibited significantlyincreased tumor growth values (Growth Index; GI) and aneuploidy/CIN compared to those bearing intact p53 (P = 0.008 for GI, P = 0.001 for CIN). The significance of these results was underscored by the fact that the latter parameters were independent of p53 within the hCdt1-hCdc6 normally expressing cases. Cumulatively, the above suggest a synergistic effect between hCdt1-hCdc6 overexpression and mutant-p53 over tumor growth and CIN in non-small-cell lung carcinomas.
TL;DR: The second-order statistics and the channel capacity of the Weibull fading channel are studied and exact closed-form expressions are derived for the average level crossing rate, the average fade duration, as well as the average Shannon's channel capacity.
Abstract: The second-order statistics and the channel capacity of the Weibull fading channel are studied. Exact closed-form expressions are derived for the average level crossing rate, the average fade duration, as well as the average Shannon's channel capacity of the Weibull fading process. Numerical results are presented to illustrate the proposed mathematical analysis and to examine the effects of the fading severity on the concerned quantities.
TL;DR: In this paper, the daily specific fecundity of anchovy stocks can vary greatly among years, areas, or seasons in response to changing environmental and trophic regimes, which may directly affect anchovy egg production.
Abstract: Since the late 1980s, the Daily Egg Production Method (DEPM) has been applied to several anchovy stocks in European waters. DEPM surveys in the Bay of Biscay were well standardized and focused on providing fisheries-independent information for stock assessment purposes. Those targeting Mediterranean stocks were largely experimental and often opportunistic, with the main aim of developing and testing the method, rather than providing estimates of spawning stock biomass (SSB) for stock assessment. Consequently, the DEPM has been applied once, twice, or a maximum of three times in certain Mediterranean areas with no among-area standardization. Different techniques for several aspects of the method have been used in the Mediterranean, and the parameters estimated vary greatly among stocks and year of application. Evidence is provided that variability in biological production among sub-basins and/or years, a characteristic of Mediterranean Sea, may directly affect anchovy egg production. The daily specific fecundity of anchovy stocks can vary greatly among years, areas, or seasons in response to changing environmental and trophic regimes. When the correlation between regression-derived estimates of daily egg production and associated estimates of daily specific fecundity for anchovy in the Mediterranean, the Bay of Biscay, and upwelling areas are compared, a significant isometric relationship emerges for the Mediterranean and the Bay of Biscay, implying density-dependent use of spawning habitat. In upwelling areas, estimates of daily egg production are relatively high for a narrow range of generally low daily specific fecundities. There is a strong linear relationship between anchovy SSB and spawning area in European waters that does not differ significantly between the Bay of Biscay and the Mediterranean Sea.
01 Jan 2004
TL;DR: This course will introduce general methods for investigating properties such as existence of solutions, reachability and decidability of hybrid systems, and how discrete “discrete” entities and concepts can coexist with continuous entity and concepts, such as differential equations.
Abstract: The aim of this course is to introduce some fundamental concepts from the area of hybrid systems, that is dynamical systems that involve the interaction of continuous (real valued) states and discrete (finite valued) states. Applications where these types of dynamics play a prominent role will be highlighted. We will introduce general methods for investigating properties such as existence of solutions, reachability and decidability of hybrid systems. The methods will be demonstrated on the motivating applications. Students who successfully complete the course should be able to appreciate the diversity of phenomena that arise in hybrid systems and how discrete “discrete” entities and concepts such as automata, decidability and bisimulation can coexist with continuous entities and concepts, such as differential equations.
TL;DR: The higher humoral immune parameters in eggs and larvae from immunised parents in comparison to eggs or larvae from non-immunised parents, suggest transfer of maternal specific and non-specific immune factors.