Showing papers by "University of Patras published in 2007"

Rethinking Organic Aerosols: Semivolatile Emissions and Photochemical Aging

Abstract: Most primary organic-particulate emissions are semivolatile; thus, they partially evaporate with atmospheric dilution, creating substantial amounts of low-volatility gas-phase material. Laboratory experiments show that photo-oxidation of diesel emissions rapidly generates organic aerosol, greatly exceeding the contribution from known secondary organic-aerosol precursors. We attribute this unexplained secondary organic-aerosol production to the oxidation of low-volatility gas-phase species. Accounting for partitioning and photochemical processing of primary emissions creates a more regionally distributed aerosol and brings model predictions into better agreement with observations. Controlling organic particulate-matter concentrations will require substantial changes in the approaches that are currently used to measure and regulate emissions.

Textile reinforced mortar (trm) versus frp as strengthening material of urm walls: out-of-plane cyclic loading

Abstract: In this study the application of a new structural material, namely textile-reinforced mortar (TRM), as a means of increasing the load carrying capacity and deformability of unreinforced masonry walls subjected to cyclic in-plane loading is experimentally investigated. The application of externally bonded TRM is considered in this work as an alternative method to the application of fiber-reinforced polymers (FRP). Hence, the effectiveness of TRM overlays is evaluated in comparison to the one provided by FRPs. Medium-scale tests were carried out on 22 masonry walls subjected to in-plane cyclic loading. Three types of specimens were used: (a) shear walls; (b) beam-columns; and (c) beams. The parameters under investigation included the matrix material (mortar versus resin), the number of textile layers and the compressive stress level applied to shear walls and beam-columns. Compared with their resin-impregnated counterparts, mortar-impregnated textiles may result in generally lower effectiveness in terms of strength, but in much higher in terms of deformability. From the results obtained in this study it is believed that TRMs hold strong promise as a solution for the structural upgrading of masonry structures under in-plane loading.

An improved limit on the axion–photon coupling from the CAST experiment

Abstract: We have searched for solar axions or similar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) set-up with improved conditions in all detectors. From the absence of excess x-rays when the magnet was pointing to the Sun, we set an upper limit on the axion–photon coupling of gaγ<8.8 × 10−11 GeV−1 at 95% CL for . This result is the best experimental limit over a broad range of axion masses and for also supersedes the previous limit derived from energy-loss arguments on globular cluster stars.

Comparative Evaluation of Various MFCC Implementations on the Speaker Verification Task

Abstract: Making no claim of being exhaustive, a review of the most popular MFCC (Mel Frequency Cepstral Coefficients) implementations is made. These differ mainly in the particular approximation of the nonlinear pitch perception of human, the filter bank design, and the compression of the filter bank output. Then, a comparative evaluation of the presented implementations is performed on the task of text-independent speaker verification, by means of the well-known 2001 NIST SRE (speaker recognition evaluation) one-speaker detection database.

Examining teachers’ beliefs about ICT in education: implications of a teacher preparation programme

Abstract: The survey presented in this article examines current teachers’ beliefs and attitudes towards information and communication technologies (ICT) in education. A total of 1165 primary and secondary education teachers participated in the study, immediately after following a training programme on basic ICT skills. The authors’ results showed that the majority of the teachers in the sample have positive attitudes towards the training programme they attended, the general role that ICT can play in education and the integration of ICT in the educational process. The authors’ findings also revealed some parameters that interfere negatively, thus making many teachers cautious of or sceptical about ICT integration in educational practice. Multivariate analysis identified three groups of teachers that exhibited a consistent approach: a group of teachers having positive attitudes towards the items of the research, a second group with negative attitudes and a third one with neutral beliefs about ICT in educatio...

Muscle and neuronal nicotinic acetylcholine receptors

Abstract: Nicotinic acetylcholine receptors (nAChRs) are integral membrane proteins and prototypic members of the ligand-gated ion-channel superfamily, which has precursors in the prokaryotic world They are formed by the assembly of five transmembrane subunits, selected from a pool of 17 homologous polypeptides (alpha1-10, beta1-4, gamma, delta, and epsilon) There are many nAChR subtypes, each consisting of a specific combination of subunits, which mediate diverse physiological functions They are widely expressed in the central nervous system, while, in the periphery, they mediate synaptic transmission at the neuromuscular junction and ganglia nAChRs are also found in non-neuronal/nonmuscle cells (keratinocytes, epithelia, macrophages, etc) Extensive research has determined the specific function of several nAChR subtypes nAChRs are now important therapeutic targets for various diseases, including myasthenia gravis, Alzheimer's and Parkinson's diseases, and schizophrenia, as well as for the cessation of smoking However, knowledge is still incomplete, largely because of a lack of high-resolution X-ray structures for these molecules Nevertheless, electron microscopy studies on 2D crystals of nAChR from fish electric organs and the determination of the high-resolution X-ray structure of the acetylcholine binding protein (AChBP) from snails, a homolog of the extracellular domain of the nAChR, have been major steps forward and the data obtained have important implications for the design of subtype-specific drugs Here, we review some of the latest advances in our understanding of nAChRs and their involvement in physiology and pathology

Personal Teaching Efficacy and Its Sources: Student Teachers' Perceptions.

Abstract: Teachers’ confidence in their ability to perform the actions that lead to student learning is one of the few individual characteristics that predicts teacher practice and student outcomes. Teachers and especially student teachers need strong efficacy beliefs in order to continue teaching during in‐service education. The current study explores the factors that precede student teachers’ beliefs of teaching efficacy and determine their conviction that they can influence instructional strategies, classroom management, and students’ engagement. In the study 198 fourth‐year students from two primary education departments in Greece completed a Teacher Efficacy Sources Inventory and a Teachers’ Sense of Efficacy Scale. It was found that self‐perceptions of teaching competence, personal characteristics, and motivation for teaching were contributory factors to teaching efficacy. The search for this type of information from student teachers is based on the assumption that feedback from students comprises a substanti...

Increased Bax/Bcl-2 ratio up-regulates caspase-3 and increases apoptosis in the thymus of patients with myasthenia gravis.

Abstract: Background: In this study the possible relation of Bax (an apoptosis promoter) to Bcl-2 (an apoptosis inhibitor) ratio with the apoptosis co-ordination enzyme, caspase-3, in the thymus of patients with myasthenia gravis (MG) was investigated in correlation with long-term clinical prognosis. Patients and Methods: The study included 46 patients (17M/29F, mean age 36.60±16.09 yr) with MG, who underwent thymectomy for treatment. The clinical staging (Osserman classification) included: stage I-5, IIA-21, IIB-17, III-3. The pathology of the thymus showed: hyperplasia-26, atrophy-8, thymoma B1 and B2 type-9, thymoma B3 type (well differentiated thymic carcinoma) -3. The patients were evaluated 39-166 (mean 91.87±38.38) months after thymectomy. At the end of the follow-up period, the patients were classified as follows: group A: complete stable remission, group B: pharmacological remission+minimal manifestations+improvement+deterioration. Paraffin sections of thymic tissue were subjected to: a) immunohistochemistry (bax, bcl-2, caspase-3 protein); b) in situ hybridization (bax, bcl-2 mRNA); and c) TUNEL-stain (apoptotic cells). Bax to bcl-2 mRNA and protein ratio was determined for each sample by dividing the %bax (+) cells by the % bcl-2 (+) cells. Results: Follow-up data were available for 39/46 patients: 13/39 patients belonged to group A and 26/39 to group B. The Bax/Bcl-2 mRNA and protein ratios were increased towards advanced disease stages (+370% for mRNA and +391% for protein, from MG stage I to stage III). These ratios were correlated with caspase-3 expression (r=0.782 and 0.583, p 1(1.47±0.07 for mRNA and 1.52±0.18 for protein). The Kaplan-Meier survival curve showed higher, free of disease, survival in group A (p=0.0082). Cox regression analysis revealed that the Bax/Bcl-2 ratio was an independent prognostic factor, however the p-value was marginally significant (95% CI:1.078-44.073, p=0.041). Conclusion: This study has demonstrated that in patients with MG who underwent thymectomy: a) the Bax/Bcl-2 ratio may up-regulate caspase-3 expression and modulate apoptosis associated with progress of the disease; b) the Bax/Bcl-2 ratio<1 was associated with complete stable remission after thymectomy; and c) Bax/Bcl-2 ratio was an independent predictive marker for therapeutic response after thymectomy. Myasthenia gravis (MG) is an autoimmune disorder caused by a defect of neuromuscular transmission due to an antibody-mediated attack upon the nicotinic acetylocholine receptors. It is characterized by fluctuating weakness that is improved by inhibitors of cholinesterase (1). Myasthenia gravis is associated with thymic hyperplasia in 65% and thymoma in 10% of cases, while MG is present in 30-45% of patients with thymomas (2). Among several therapeutic modalities employed in the treatment of MG, thymectomy is one of the efficient strategies used in the integrated management of the disease (3-5). Today it is well-known that apoptosis maintains homeostasis in living organisms by depleting cells as a response to various stimuli (6). After cell depletion due to apoptosis, tissue remodelling is achieved through cell proliferation and the degree of this remodelling depends on the balance between apoptosis and proliferation. Apoptosis is a morphologically distinct, gene-directed form of cell death characterized by cytoplasmic fragmentation and nuclear condensation that contributes to both physiological and pathological processes (7). Previous studies have

Recent decline in precipitation and tree growth in the eastern Mediterranean

Abstract: We present evidence of a recent drying in the eastern Mediterranean, based on weather and tree-ring data for Samos, an island of the eastern Aegean Sea. Rainfall declined rapidly after the late 1970s following trends for the entire Mediterranean and was associated with reduced tree-ring width in Pinus brutia. The most recent decline led to the lowest annual radial stem increment after the last 100 years (as far as records reach). As moisture availability decreased best correlations of tree growth with rainfall were obtained for progressively longer integration periods (1–2 years in moister periods, 5–6 years during the severe dryness of 20th century's last decades), suggesting increasing dependency in deep soil water. Such long-term integration periods of tree-growth responses to precipitation have not been reported before. They may reflect a tree-rooting pattern adapted to cope with even several successive dry years. In late summer 2000, moisture reserves became exhausted, however, and a substantial fraction of low altitude pines died, including some 80-year-old trees, which underlines the exceptional extent this trend had reached. Our findings provide empirical support for Intergovernmental Panel on Climate Change projections derived from global circulation models that the Mediterranean, its eastern basin in particular, should become drier as temperature rises, as was the case in the recent past.

Sensitivity of PM 2.5 to climate in the Eastern US: a modeling case study

Abstract: . The individual effects of various meteorological parameters on PM2.5 concentrations in the Eastern US are examined using the PMCAMx chemical transport model so that these effects and their relative magnitudes can be better understood. A suite of perturbations in temperature, wind speed, absolute humidity, mixing height, cloud cover, and precipitation are imposed individually on base case conditions corresponding to periods in July 2001 and January 2002 in order to determine the sensitivities of PM2.5 concentrations and composition to these separate meteorological parameters. Temperature had a major effect on average PM2.5 in January (−170 ng m−3 K−1) due largely to the evaporation of ammonium nitrate and organic aerosol at higher temperatures; increases in sulfate production with increased temperature counteracted much of this decrease in July. Changes in mixing height also had major effects on PM2.5 concentrations: 73 ng m−3 (100 m)−1 in January and 210 ng m−3 (100 m)−1 in July. Changes in wind speed (30 to 55 ng m−3 %−1) and absolute humidity (15 to 20 ng m−3 %−1) also had appreciable effects on average PM2.5 concentrations. Precipitation changes had large impacts on parts of the domain (a consequence of the base case meteorology), with sensitivities to changing area of precipitation in July up to 100 ng m−3 %−1. Perturbations in cloud cover had the smallest effects on average PM2.5 concentrations. The changes in PM2.5 concentrations resulting from changing all eight meteorological parameters simultaneously were approximately within 25% or so of the sum of the changes to the eight individual perturbations. The sensitivities of PM2.5 concentrations to changes in these meteorological parameters indicate that changes in climate could potentially have important impacts on PM2.5 concentrations.

Electronic structure and nonlinear optical rectification in a quantum dot: effects of impurities and external electric field

Abstract: The electronic structure of a spherical quantum dot with parabolic confinement that contains a hydrogenic impurity and is subjected to a DC electric field is studied. In our calculations we vary the position of the impurity and the electric field strength. The calculated electronic structure is further used for determining the nonlinear optical rectification coefficient of the quantum dot structure. We show that both the position of the impurity and the strength of the electric field influence the nonlinear optical rectification process.

Ammonia Emission Controls as a Cost-Effective Strategy for Reducing Atmospheric Particulate Matter in the Eastern United States

Abstract: Current regulation aimed at reducing inorganic atmospheric fine particulate matter (PM2.5) is focused on reductions in sulfur dioxide (SO2) and oxides of nitrogen (NO(x) = NO + NO2); however, controls on these pollutants are likely to increase in cost and decrease in effectiveness in the future. A supplementary strategy is reduction in ammonia (NH3) emissions, yet an evaluation of controls on ammonia has been limited by uncertainties in emission levels and in the cost of control technologies. We use state of the science emission inventories, an emission-based regional air quality model, and an explicit treatment of uncertainty to estimate the cost-effectiveness and uncertainty of ammonia emission reductions on inorganic particulate matter in the Eastern United States. Since a paucity of data on agricultural operations precludes a direct calculation of the costs of ammonia control, we calculate the "ammonia savings potential", defined as the minimum cost of applying SO2 and NO(x) emission controls in order to achieve the same reduction in ambient inorganic PM2.5 concentration as obtained from a 1 ton decrease in ammonia emissions. Using 250 scenarios of NH3, SO2, and NO(x) emission reductions, we calculate the least-cost SO2 and NO(x) control scenarios that achieve the same reduction in ambient inorganic PM2.5 concentration as a decrease in ammonia emissions. We find that the lower-bound ammonia savings potential in the winter is $8,000 per ton NH3; therefore, many currently available ammonia control technologies are cost-effective compared to current controls on SO2 and NO(x) sources. Larger reductions in winter inorganic particulate matter are available at lower cost through controls on ammonia emissions.

Textile-Reinforced Mortar versus Fiber-Reinforced Polymer Confinement in Reinforced Concrete Columns

Abstract: Poorly detailed reinforced concrete (RC) columns have limited deformation capacity under seismic loads due to buckling of the longitudinal bars. This study experimentally investigates the effectiveness of textile-reinforced mortar (TRM) jackets as a means of confining these columns. The effectiveness of TRM is evaluated by comparing TRM jackets with fiber-reinforced polymer (FRP) jackets of equal stiffness and strength. Tests were carried out both on short prisms under concentric compression and on nearly full-scale, nonseismically detailed, RC columns subjected to cyclic uniaxial flexure under constant axial load. The compression tests on 15 RC prisms show that TRM jackets provide a substantial gain in compressive strength and deformation capacity by delaying buckling of the longitudinal bars. This gain increases with the volumetric ratio of the jacket. Compared with their FRP counterparts, TRM jackets used in this study are slightly less effective in terms of increasing strength and deformation capacity by approximately 10%. Tests on nearly full-scale columns under cyclic uniaxial flexure show that TRM jacketing is very effective (and equal to the FRP jacketing) as a means of increasing the cyclic deformation capacity and the energy dissipation of RC columns with poor detailing by delaying bar buckling.

Time-series methods for fault detection and identification in vibrating structures

Abstract: An overview of the principles and techniques of time-series methods for fault detection, identification and estimation in vibrating structures is presented, and certain new methods are introduced. The methods are classified, and their features and operation are discussed. Their practicality and effectiveness are demonstrated through brief presentations of three case studies pertaining to fault detection, identification and estimation in an aircraft panel, a scale aircraft skeleton structure and a simple nonlinear simulated structure.

Renal failure in multiple myeloma: incidence, correlations, and prognostic significance.

Abstract: Renal failure (RF) is a common and severe complication of patients with multiple myeloma (MM). The purpose of our study was to assess the incidence of RF in a contemporary series of newly diagnosed patients with MM, its association with specific clinical and laboratory features, and its impact on patients' outcome. Over the last decade, 756 newly diagnosed symptomatic patients with MM were included in our database. Renal failure, defined as a serum creatinine ≥ 2 mg/dl at the time of diagnosis, was seen in 21% of patients. Multiple parameters were associated with RF, but logistic regression analysis showed that RF was independently associated only with International Staging System and Bence Jones proteinuria. The presence of RF was associated with a trend for higher early death rate but with a similar response to primary therapy. The median survival of patients with RF was 19.5 months versus 40.4 months for patients without RF (p < 0.001). Several variables were associated with impaired survival by univar...

Pure versus metal-ion-doped nanocrystalline titania for photocatalysis

Abstract: Thin films of pure or doped nanocrystalline titania have been deposited on glass slides by using a sol–gel procedure, in the presence of surfactant Triton X-100, which acts as template of the nanostructure. Fe3+, Cr3+ and Co2+ were used as dopants while the doping extended in a broad domain from very low to very high levels. The photocatalytic efficiency of pure or doped titania was tested for discoloration of an aqueous solution of Basic Blue 41. The presence of dopants resulted in a progressive loss of total crystallinity, some transition from anatase into rutile and, in the case of Co2+, formation of the mixed oxide cobalt titanate. Loss of anatase had dramatic consequences on photocatalytic efficiency by UV–vis excitation, which decreased fast with increasing dopant concentration. Selected visible excitation of the doped titania could lead to photodegradation of the dye but to a far lesser degree than UV–vis excitation. Photosensitization by absorption of light by the dye itself loses its importance in the presence of the dopant. Thus the doped material is a visible-light photocatalyst but substantial photodegradation efficiency is achieved only at very high doping levels, for example, 20 at.% for Fe3+ doping. In any case, direct UV excitation of pure titania is a more efficient photocatalytic process than visible excitation of the doped semiconductor.

Angiopoietin-2 is increased in severe sepsis: correlation with inflammatory mediators.

Abstract: Objective:Angiopoietin (Ang)-2 is an endothelium-specific growth factor, regulated by proinflammatory stimuli, that destabilizes vascular endothelium and increases vascular leakage; consequently, Ang-2 may contribute to sepsis pathophysiology. We have studied 1) serum Ang-2 levels in critically-ill

Hydrogen production by photocatalytic alcohol reforming employing highly efficient nanocrystalline titania films

Abstract: Hydrogen production by photocatalytic alcohol reforming has been studied in the presence of a Pt/TiO2 photocatalyst. Nanocrystalline titania was deposited on glass slides by using a sol–gel process in the presence of surfactant template. Band-gap excitation of titania was made by using a low-energy Black-Light source. Water–ethanol mixtures proved the most efficient substrate for hydrogen production. This system demonstrated an impressive efficiency, which reached up to 74% active electron to incident photon ratio and 32% energy conversion efficiency.