Showing papers by "University of Patras published in 1996"

The role of loneliness and social support in adjustment to loss: A test of attachment versus stress theory

Abstract: A longitudinal study of a matched sample of 60 recently widowed and 60 married men and women tested predictions from stress and attachment theory regarding the role of social support in adjustment to bereavement. Stress theory predicts a buffering effect, attributing the impact of bereavement on well-being to stressful deficits caused by the loss and assuming that these deficits can be compensated through social support. In contrast, attachment theory denies that supportive friends can compensate the loss of an attachment figure and predicts main effects of marital status and social support. Attachment theory further suggests that marital status and social support influence well-being by different pathways, with the impact of marital status mediated by emotional loneliness and the impact of social support mediated by social loneliness. Results clearly supported attachment theory.

Carbon dioxide reforming of methane to synthesis gas over Ni/La2O3 catalysts

Abstract: Carbon dioxide reforming of methane to synthesis gas was studied employing Ni/La2O3 catalysts. It was found that, in contrast to the performance of other nickel-based catalysts (e.g. Ni/Al2O3 and Ni/CaO) which exhibit continuous deactivation with time on stream, the rate over the Ni/La2O3 catalyst increases during the initial 2–5 h of reaction and then tends to be essentially invariable with time on stream, displaying very good stability. X-ray diffraction (XRD) studies reveal that a large CO2 pool, stored in the form of La2O2CO3, is accumulating on the Ni/La2O3 catalyst, following exposure to the CH4/CO2 mixture at reaction conditions. Results of H2- and CO-temperature-programmed desorption reveal that the HNi bond is weakened and CO disproportionation is unfavoured on the Ni/La2O3 catalyst, as compared to the Ni/Al2O3 catalyst. Comparison of H2 and CO uptake and Ni dispersion by XRD shows that H2 and CO uptakes are significantly suppressed, by ca. 3–10 times, suggesting that a large portion of the Ni surface is blocked by lanthanum species. It is proposed that the interaction between Ni crystallites and La2O3 support or La species which are decorating the Ni crystallites is responsible for the unusual chemisorptive and catalytic behaviour observed over the Ni/La2O3 catalyst.

Inhibition of photosynthesis in olive trees (Olea europaea L.) during water stress and rewatering

Abstract: mwn,,«», The effect of high levels of natural light on leaf photosynthesis in olive trees (Olea europaea L. var. Coratina), grown in pots outdoors in the summer and subjected to water stress, was studied. Net photosynthetic rates reached maximum values early in the morning in both control and stressed plants and subsequently declined gradually. This inactivation of photosynthetic activity was accompanied by changes in the fluorescence characteristics of the upper intact leaf surface. The maximum fluorescence yield (Fp) and the ratio Fv/Fp decreased at midday especially in water-stressed plants, but the initial fluorescence (Fo) rose to a maximum value at midday and declined again in the afternoon. In control plants the values of maximum fluorescence Fp and the ratio Fv/Fp increased again in the afternoon and had recovered almost completely by 8 p.m. as the leaf water potential recovered. In stressed plants this diurnal recovery was not complete, so that the photosynthetic rates and the ratio Fv/Fp declined gradually during the development of water stress. These results indicate that in olive trees subjected to severe water stress the non-stomatal component of photosynthesis was affected and perhaps a light-dependent inactivation of the primary photochemistry associated with photosystem II (PSII) occurred. Four to five days after rewatering severely stressed plants, the predawn leaf water potential, net photosynthetic rates and chlorophyll fluorescence indices recovered only partially.

Immune response in insects: the role of phenoloxidase in defense reactions in relation to melanization and sclerotization.

Abstract: It is well known that activated prophenoloxidase (proPO) plays an important role in cuticular melanization and sclerotization. In addition, studies dealing with immune response of insects suggest that phenoloxidase (PO) is also critical in the defense reactions of insects against invaders. proPO is activated by elicitors derived from microbial cell wall components such as peptidoglycan, beta-1,3-glucan, and lipopolysaccharide (LPS). According to our recent studies we proposed a model clarifying the role of PO in both cellular and humoral immune responses. LPS triggers Ceratitis capitata hemocytes via induced protein tyrosine phosphorylation to release biologically active molecules, including p47 and proPO-activators. Furthermore, hemocytes in response to LPS facilitate clearance of LPS from the hemocoel of medfly. The effector molecules involved in the LPS clearance are hemocyte surface-associated p47 (mp47), soluble p47 (sp47), activated proPO, and tyrosine. A similar LPS clearance system in the integument of medfly in vitro was also demonstrated. According to our data, the proposed mechanism for LPS clearance from hemocoel and from integument is the crosslinking of LPS to p47 or certain integumental proteins via the intermediacy of reactive tyrosine derivatives generated by PO activity, as is the case for cuticular protein-chitin crosslinks during sclerotization. We also demonstrated that metabolites of the eumelanin biosynthesis and not melanin itself or N-acetyldopamine (NADA), the key precursor of sclerotizing agent, were necessary for the immune responses by hemocytes and integument.

Towards an adaptive natural language interface to command languages

Abstract: Operating system command languages assist the user in executing commands for a significant number of common everyday tasks. On the other hand, the introduction of textual command languages for robots has provided the opportunity to perform some important functions that leadthrough programming cannot readily accomplish. However, such command languages assume the user to be expert enough to carry out a specific task in these application domains. On the contrary, a natural language interface to such command languages, apart from being able to be integrated into a future speech interface, can facilitate and broaden the use of these command languages to a larger audience. In this paper, advanced techniques are presented for an adaptive natural language interface that can (a) be portable to a large range of command languages, (b) handle even complex commands thanks to an embedded linguistic parser, and (c) be expandable and customizable by providing the casual user with the opportunity to specify some types of new words as well as the system developer with the ability to introduce new tasks in these application domains. Finally, to demonstrate the above techniques in practice, an example of their application to a Greek natural language interface to the MS-DOS operating system is given.

Mechanistic aspects of carbon dioxide reforming of methane to synthesis gas over Ni catalysts

Abstract: A study of the kinetic isotope effect (CH4/CO2→ CD4/CO2) for carbon dioxide reforming of methane to synthesis gas shows that an isotope effect exists with kCH 4/kCD 4 ratio of 1.05–1.97, depending on reaction temperature and catalyst applied. The attainment of stable performance over Ni/La2O3 catalyst is found to be related to the strong chemisorption of CO2, weak chemisorption of CH4 and slow rate of CHx formation, and fast rate for CHx removal by oxidation.

Partial oxidation of methane to synthesis gas via the direct reaction scheme over Ru/TiO2 catalyst

Abstract: The partial oxidation of methane to synthesis gas has been investigated over various supported metal catalysts. The effects of operational variables on mass and heat transport resistances were investigated for defining the kinetic regime. It is observed that, in the absence of significant mass and heat transfer resistances, high selectivity (up to 65%) to synthesis gas is obtained over Ru/TiO2 catalysts in the low methane conversion range (\(X_{O_2 }< 100\% \)) whereas only negligibly small selectivity to synthesis gas is observed over all other catalysts investigated under similar conditions. This indicates that the Ru/TiO2 catalyst possesses unique properties, offering high selectivity to synthesis gas formation via the direct reaction scheme, whereas the other catalysts promote the sequence of total oxidation of methane to CO2 and H2O, followed by reforming reactions to synthesis gas. An increase of selectivity to synthesis gas, in the presence of oxygen, is achieved over the Ru/TiO2 catalyst by multi-feeding oxygen, which is attributed to suppression of deep oxidation of H2 and CO.

Network simulation of steady-state two-phase flow in consolidated porous media

Abstract: Multiphase flow in porous media is a complex process encountered in many fields of practical engineering interest, such as oil recovery from reservoir rocks, aquifer pollution by liquid wastes and soil reconstitution, and agricultural irrigation. A computer-aided simulator of steady-state two-phase flow in consolidated porous media is developed. The porous medium is modeled as a 3-D pore network of suitably shaped and randomly sized unit cells of the constricted-tube type. The problem of two-phase flow is solved using the network approach. The wetting phase saturation, the viscosity ratio, the capillary number, and the probability of coalescence between two colliding ganglia are changed systematically, where as the geometrical and topological characteristics of the porous medium and wettability (dynamic contact angles) are kept constant. In the range of the parameter values investigated, the flow behavior observed is ganglion population dynamics (intrinsically unsteady, but giving a time-averaged steady state). The mean ganglion size and fraction of the nonwetting phase in the form of stranded ganglia are studied as functions of the main dimensionless parameters. Fractional flows and relative permeabilities are determined and correlated with flow phenomena at pore level. Effects of the wetting phase saturation, the viscosity ratio, the capillary number, and themore » coalescence factor on relative permeabilities are examined.« less

Soluble, Rigid-Rod Polyamide, Polyimides, and Polyazomethine with Phenyl Pendent Groups Derived from 4,4''-Diamino-3,5,3'',5''-tetraphenyl-p-terphenyl

Abstract: The reaction of 4,4‘-(1,4-phenylene)bis(2,6-diphenylpyrylium tetrafluoroborate) with nitromethane afforded 4,4‘‘-dinitro-3,5,3‘‘,5‘‘-tetraphenyl-p-terphenyl, which was catalytically hydrogenated to the corresponding diamine. The latter was used as starting material for the preparation of new rigid-rod polyamide, polyimides, and polyazomethine bearing phenyl pendent groups as well as the respective model compounds. Characterization of polymers was accomplished by inherent viscosity measurements, elemental analysis, 1H-NMR, 13C-NMR, X-ray, DTA, TMA, TGA, and isothermal gravimetric analysis. The polymers were amorphous and soluble in polar aprotic solvents. Polyamide showed an outstanding solubility, being soluble even in o-dichlorobenzene and chloroform. Polyamide displayed Tg and softening temperature at 135 and 155 °C, respectively, whereas other polymers showed only Tg above 265 °C. The polymers were stable up to 397−441 °C in N2 and 344−363 °C in air and afforded anaerobic char yields of 68−77% at 800 °...

Surface and grain-boundary energies in yttria-stabilized zirconia (YSZ-8 mol%)

Abstract: The multiphase equilibration technique has been used to measure the equilibrium angles that develop at the interphase boundaries of a solid-liquid-vapour system after annealing and also the surface (γsv)and the grain-boundary, (γss) energies of polycrystalline yttria-stabilized zirconia (8 mol% Y2O3). The data was recorded in the temperature range 1573–1873 K. Linear temperature functions were obtained for the surface energy $$\gamma _{SV} (Jm^{ - 2} ) = 1.927 - 0.428x10^{ - 3} T$$ and for the grain-boundary energy $$\gamma _{SS} (Jm^{ - 2} ) = 1.215 - 0.358x10^{ - 3} T$$

Age-related changes in the content of the C-terminal region of aggrecan in human articular cartilage

Abstract: The content of the C-terminal region of aggrecan was investigated in samples of articular cartilage from individuals ranging in age from newborn to 65 years. This region contains the globular G3 domain which is known to be removed from aggrecan in mature cartilage, probably by proteolytic cleavage, but the age-related changes in its abundance in human cartilage have not been described previously. The analysis was performed by immunosorbant assay using an antiserum (JD5) against recombinant amino acid residues of human aggrecan, on crude extracts of cartilage without further purification of aggrecan. The results showed that the content of the C-terminal region decreased with age relative to the G1 domain content (correlation coefficient = 0.463). This represented a 92% fall in the content of this region of the molecule from newborn to 65 years of age. furthermore, when the G1 content of the cartilage extracts was corrected to only include the G1 attached to aggrecan and to exclude the G1 fragments which accumulate as a by-product of normal aggrecan turnover (free G1), the age-related decrease in the C-terminal region remained very pronounced. Analysis by composite agarose/PAGE showed that the number of subpopulations of aggrecan resolved increased from one in newborn to three in adult cartilage. All of these reacted with an antiserum to the human G1 domain, but only the slowest migrating species reacted with the C-terminal region antiserum (JD5). Similar analysis by SDS/PAGE confirmed the presence of high-molecular-mass (200 kDa) proteins reactive with JD5, but no reactive fragments of lower electrophoretic mobility were detected. In contrast, when probed with the antiserum to the human G1 domain, the immunoblots showed protein species corresponding to the free G1 and G1-G2 fragments, which were present at high concentrations in adult cartilage. The results suggest that the loss of the C-terminal region is not directly part of the process of aggrecan turnover, but it is a slow independent matrix process that occurs more extensively with aging as turnover rates become slower. Young cartilage with the fastest turnover contains least molecules lacking the C-terminal region, whereas in old tissue with slow turnover few molecules retain this region. An increase in the cleavage of this region with age may also contribute to this change. The content of the C-terminal region may thus give a measure of the abundance of newly synthesized aggrecan.

The Electrochemical Activation of Catalytic Reactions

Abstract: The use of electrochemistry to activate and precisely tune heterogeneous catalytic processes is a new development1-7 which originally emerged due to the existence of solid electrolytes. Depending on their composition, these specific anionic or cationic conductor materials exhibit substantial electrical conductivity at temperatures between 25 and 1000°C. Within this broad temperature range, which covers practically all heterogeneous catalytic reactions, solid electrolytes can be used as reversible in situ promoter donors or poison acceptors to affect the catalytic activity and product selectivity of metals deposited on solid electrolytes in a very pronounced, reversible, and, to some extent, predictable manner.

Structural and seismological segmentation of the Gulf of Corinth fault system: implications for models of fault growth

Abstract: The positions and dimensions of fault segments within the Gulf of Corinth fault system have been identified by analysing spatial variation in fault displacements and fault kinematics. Growth of these fault segments is assessed by comparing their geometry and kinematics with the geometry and kinematics of the three sets of earthquake surface ruptures that are known to have affected the area in the last -200 years. Areas along the Gulf of Corinth fault system exhibiting low fault displacement (tens of metres) are identified as persistent segment boundaries which separate the fault system into a number of fault segments characterised by displacements which achieve maxima of -3 km. Fault-slip directions defined by lineations on fault planes vary systematicalIy with fault displacement, showing a converging pattem towards the hanging-walls of the fault segments: the fault-slip directions change by -90° across persistent segment boundaries. It is unclear where fault segments end and persistent segment boundaries begin, but if the persistent segment boundaries are considered to be -10-15 km across, the intervening fault segments achieve lengths of 30-35 km. In contrast known surface ruptures during the last -200 years, including those for the 1995 Egion earthquakes, have all been < 15 km in Length. these so-caIled earthquake segmens are, therefore, considerably shorter than the fault segmentss that hosted the earthquakes. Also, the positions of earthquake segments have varied relative to the positions of the fault segments during successive earthquakes. It appears, therefore, that a Modified Overlap Model is more appropriate than the Characteristic Earthquake Model to describe the seismological behaviour of fault segments around the Gulf of Corinth through a number of earthquake cycles. A pattern of coseismic slip vectors converging towards the hanging-wall has been measured for the surface ruptures to 1995 Egion earthquakes; a similar pattern was noted for the 1981 Alkyonides earthquake ruptures. Repetition of such ruptures in different positions along fault segments, in accordance with a Modified Overlap Model, will produce systematic variations in the scatter of fault-slip directions, with fault displacement. Thus, scatter in the orientations of lineations on fault planes may contain information concerning the lengths and positions of numerous pre-historic earthquake segments; information which may be used to constrain both the palaeoseismology and the future seismjcity in areas of active extension.

Soluble interleukin‐6 receptor (sIL‐6R), a new prognostic factor in multiple myeloma

Abstract: sIL-6R is a 55 kD soluble molecule mediating the interleukin-6 (IL-6) signal through the IL-6 receptor-associated transmembrane signal transducer, gp130. It has recently been suggested that sIL-6R serum levels may reflect disease severity in multiple myeloma (MM). We determined sIL-6R serum levels in 25 normal controls (NC) and in 80 MM patients at diagnosis and during the course of the disease. Measurements were done by ELISA. In NC, sIL-6R levels ranged from 14 to 40 ng/ml (median 28 ng/ml) whereas in MM patients the range was 10–200 ng/ml (median 38 ng/ml) (P < 0.01). 61 patients entered remission and 19 were resistant. Median sIL-6R value at diagnosis was 36 ng/ml (10–120) in responding patients, and 82 ng/ml (20–200) in non-responding patients (P < 0.001). During a follow-up from 12 to 89 months, sIL-6R values remained more or less stable in most patients. High sIL-6R levels correlated with poor survival.

Some Studies on Dual Reciprocity BEM for Elastodynamic Analysis

Abstract: The accuracy of the dual reciprocity boundary element method for two-dimensional elastodynamic interior problems is investigated. A general analytical method is described for the closed form determination of the displacement and traction tensor corresponding to radial basis functions and explicit expressions of these tensors are provided for a number of specific basis functions. For all these basis functions the accuracy of the dual reciprocity boundary element method is numerically assessed for three interior plane stress elastodynamic problems. The influence of internal points on the accuracy of the solution is also considered. Useful results concerning the suitability of the various basis functions for solving plane elastodynamic problems are obtained.

High performance capillary electrophoresis method to characterize heparin and heparan sulfate disaccharides

Abstract: A rapid, sensitive and accurate high-performance capillary electrophoresis method is described for the determination of the sulfation pattern of heparin and heparan sulfate disaccharides. The analysis, performed after enzymic degradation of the polysaccharides with heparinase and heparinases II and III in combination, yields highly UV-absorbing Δ-disaccharides. The separation is performed with reversed polarity using 15 mM phosphate buffer, pH 3.50. This method is superior to others since all known 12 disaccharides carrying N-acetylated, N-sulfated or unsubstituent glucosamine can be separated in a single run of 15 min. At the highest sensitivity the analysis consumes only a few femtograms of glycosaminoglycan and allows a determination of Δ-disaccharides at the attomole level.