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Showing papers by "University of Patras published in 1981"


Journal ArticleDOI
TL;DR: In this paper, the effects of Gr (Grashof number), Gm (modified Grashof numbers) and permeability K of the porous medium on the velocity and rate of heat transfer are discussed when the surface is subjected to a constant suction velocity.

119 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of a circumferential crack on the torsional dynamic behavior of a shaft is studied, and the results show that the change in dynamic response due to the crack is high enough to allow detection of the crack and estimation of its location or magnitude.

89 citations



Journal ArticleDOI
TL;DR: It is proved that under appropriate but reasonable conditions the expressions of the unknown function of the integral equation, resulting from the natural interpolation formulae of the direct method, as well as of the Nyström method, are identical along the whole integration interval.
Abstract: A Cauchy type singular integral equation of the first kind can be numerically solved either directly, through the use of a Gaussian numerical integration rule, or by reduction to an equivalent Fredholm integral equation of the second kind, where the Nystrom method is applicable. In this note it is proved that under appropriate but reasonable conditions the expressions of the unknown function of the integral equation, resulting from the natural interpolation formulae of the direct method, as well as of the Nystrom method, are identical along the whole integration interval.

47 citations


Journal ArticleDOI
TL;DR: In this paper, the surface sediments have been classified into four major Provinces, as follows: (1) Province 1 ( shelf muds; (2) Province 2 ( muddy sands; (3) Province 3 (outer margin muds); and (4) Province 4 (outer shelf/shelf break).

40 citations


Journal ArticleDOI
TL;DR: The Acheloos and small Evinos deltas have been occupied for at least 2300 years and air photographs show three former major distributary channels were occupied by at least 5,000 years.

40 citations


Journal ArticleDOI
TL;DR: Quadrature rules for the approximate evaluation of derivatives of Cauchy principal value integrals can be obtained by formal differentiations of the right sides of the corresponding quadrature rules (without derivatives).
Abstract: Quadrature rules for the approximate evaluation of derivatives of Cauchy principal value integrals (with respect to the free variable inside the integral) can be obtained by formal differentiations of the right sides of the corresponding quadrature rules (without derivatives) The justification of this method, under appropriate conditions, is presented in this short communication The results of this short communication are also applicable to the numerical evaluation of a class of finite-part integrals and to the numerical solution of singular integrodifferential equations

34 citations


Journal ArticleDOI
TL;DR: Two independent sedimentation FFF methods are presented to characterize bovine serum albumin microspheres in terms of particle size, polydispersity, and diffusion coefficient.

34 citations


Journal ArticleDOI
TL;DR: In this article, the authors considered two-dimensional unsteady free convection and mass transfer, flow of an incompressible viscous dissipative and electrically conducting fluid past an infinite, vertical porous plate, when the flow, is subjected in the action of uniform transverse magnetic field.
Abstract: Two-dimensional unsteady free convection and mass transfer, flow of an incompressible viscous dissipative and electrically conducting fluid, past an infinite, vertical porous plate, is considered, when the flow, is subjected in the action of uniform transverse magnetic field. The magnetic Reynolds number is taken to be small enough so that the induced magnetic field is negligible. The solution of the problem is obtained in the form of power series of Eckert numberE, which is very small for incompressible fluids. Analytical expressions for the velocity field and temperature field are given, as well as for the skin friction and the rate of heat transfer for the case of the mean steady flow and for the unsteady one. The influence of the magnetic parameter,M, modified Grashof numberG c , Schmidt numberS c and frequency ω, on the flow field, is discussed with the help of graphs, when the plate is being cooled, by the free convection currents (G r ,E>0), or heated (G r ,E<0). A comparative study with hydrodynamic case (M=0) and the hydromagnetic one (M≠0) is also made whenever necessary.

34 citations




Journal ArticleDOI
01 Jan 1981
TL;DR: It is evident from the in vivo and organ culture studies, that the major haemolymph proteins are synthesized during the late larval stage and their synthesis declines abruptly during the stage of white pupae.
Abstract: The accumulation of major haemolymph proteins (a group of proteins immunologically related to Calliphorin) their biosynthesis in vivo and in organ culture as well as their secretion, has been studied during the late larval stages and white pupae of the Mediterranean fruit flyCeratitis capitata. The accumulation of major haemolymph proteins in the haemolymph, shows a twenty fold increase from the 4-day old larvae to the white pupae stage, while in the fat body there is only a seven fold increase. It is evident from the in vivo and organ culture studies, that the major haemolymph proteins are synthesized during the late larval stage and their synthesis declines abruptly during the stage of white pupae. It seems also that each polypeptide has its own characteristic developmental kinetics of synthesis. The major haemolymph proteins are synthesized in the fat body and are very quickly secreted into the haemolymph.


Journal ArticleDOI
TL;DR: In this paper, a new method of numerical solution of singular integral equations with Cauchy type kernels is proposed, based on the replacement of the unknown function by another function, and an application of the method to a crack problem in plane elasticity is also made.
Abstract: The solution of many elasticity problems and particularly crack problems can be reduced to the solution of a singular integral equation with a Cauchy type kernel (or a system of such equations). In this paper a new method of numerical solution of singular integral equations with Cauchy type kernels is proposed, based on the replacement of the unknown function by another function. This method presents some advantages over the previous methods under appropriate conditions. An application of the method to a crack problem in plane elasticity is also made.

Journal ArticleDOI
TL;DR: A comparative study of two male recombination factors isolated from the same Southern Greek natural population, revealed specific differences in their activities, suggesting premeiotic origin.
Abstract: A comparative study of two male recombination factors (31. 1 MRF and 23. 5 MRF) isolated from the same Southern Greek natural population, revealed specific differences in their activities. 23. 5 MRF induces female sterility due to atrophie ovaries at a wide range of temperatures while 31. 1 MRF does so only at high temperatures. The gross morphology of the atrophie ovaries was the same and unilaterally affected pairs were found in the F 1 of crosses with both 23. 5 and 31. 1 MRF. Furthermore, 23. 5 MRF induces: ( a ) lower frequencies of abnormal anaphases I and II than 31. 1 MRF, ( b ) higher frequencies of ‘double crossovers’ resulting from deficiences or duplications, ( c ) large clusters of recombinants, suggesting premeiotic origin and ( d ) cases where one of the non-recombinant phenotypes was not produced. Such cases have never been observed with 31. 1 MRF. Moreover, the cytoplasm of the Cy L 4 /Pm strain that suppresses 31. 1 MRF does not affect the activities of 23. 5 MRF. Hypotheses to explain the different behaviour of the two factors are presented and discussed.


Journal ArticleDOI
TL;DR: In this paper, the authors report a study of the setting time of concrete as a function of mixing water and the results are presented diagrammatically, where the set of experiments, in which four concrete mixes were used, were designed, the only difference being in the quantity of the mixing water in each mix.

Journal ArticleDOI
TL;DR: In this paper, the main result needed to complete Hirseh's proof, which is exactly what is needed for the complete proof, is the following: the Stiefel-Whitney class of the universal oriented bundle is an element of BSO.
Abstract: Theorem 1. I / n ~_ 5, then any n-dimensional mani/old which is the boundary o/a~ orientable mani/old will be also the boundary o / a simple connected manifold which imbeds in R 2n-i. In [4] M. Hirsch proved the Theorem above for many values of n, depending upon the dyadic expansion of n. By "manifold" we mean a compact C ~~ manifold. Let y be a cohomology class of the classifying space BSO, with any group of coefficients and let W be an oriented manifold, (with boundary or not). Then y(W) will denote the corresponding normal characteristic class of W. By Wi we denote the/-dimensional Stiefel-Whitney class of the universal oriented bundle. I f i equals 1 or an even number, then Wi is an element of H i (BSO; Z2). On the other hand ff i is an odd number greater than 1, then Wi is an element of H i (BSO; Z). Let wi be the rood 2 reduction of Wi. The main result of this paper, which is exactly what is needed to complete Hirseh's proof, is the following:

Journal ArticleDOI
TL;DR: In this article, the dynamic mechanical properties of polyblends of a polyurethane (PU) elastomer and polyvinylchloride (PVC) at five compositions were studied at 110 Hz, between −120 and 120°C.
Abstract: The dynamic mechanical properties of polyblends of a polyurethane (PU) elastomer and poly(vinylchloride) (PVC) at five compositions were studied at 110 Hz, between −120 and 120°C. The study also included tensile testing at 25°C, and examination of polyblend morphology and fire-retardant properties. The results were analyzed using suitable two-phase mechanics models valid for such systems. This analysis, together with the morphological evidence and the thermomechanical spectra, indicate that these polymer alloys are essentially heterogeneous and their useful mechanical properties are due to good adhesion between the two phases. This conclusion is also corroborated by the tensile properties study. Fire retardancy is significant only above ∼60% by weight of PVC.

Journal ArticleDOI
TL;DR: In this article, sediment cores from the western part of the North Aegean Sea Trough were examined and three distinct lithofacies were identified, which correspond with similar environments identified elsewhere in the western and southeastern Mediterranean.


Journal ArticleDOI
TL;DR: In this paper, an iterative method for the numerical solution of singular integral equations of the first kind with Cauchy-type kernels is proposed, based on the Gauss- and Lobatto-Chebyshev quadrature rules.


Journal ArticleDOI
TL;DR: In this article, the authors extend Chandrasekhar's perturbation theory to include third-order terms in the perturbations parameter, which is required for a subsequent numerical treatment of the structure determination.
Abstract: In order to specify the structure of a rapidly and differentially rotating gaseous polytrope, we extend Chandrasekhar's perturbation theory to include third-order terms in the perturbation parameter. In the present paper, the theory developed is required for a subsequent numerical treatment of the structure-determination.

Book ChapterDOI
01 Sep 1981
TL;DR: In this paper, the authors studied the mechanism of bifurcation of three-dimensional periodic orbits from the plane of motion of the primaries and described suitable numerical techniques for their accurate determination and for their continuation through the range of the mass parameter of the problem.
Abstract: We study the mechanism of bifurcation of three-dimensional periodic orbits from the plane of motion of the primaries. The branchings of simple and double periodic three-dimensional orbits occur at the plane periodic orbits of indifferent vertical stability. These vertical-critical plane orbits are doubly important. Not only are they necessary in order to specify the vertically stable segments of the families of plane periodic orbits, but they are also the starting points of the families of the simplest possible three-dimensional periodic orbits, namely, the simple and double periodic. We describe here suitable numerical techniques for their accurate determination and for their continuation through the range of the mass parameter μ of the problem. We use these techniques to determine the first few vertical-critical orbits of the basic families of periodic orbits of the problem, namely, families l, m, i, h, a, b and c, for the entire range of μ. The initial conditions of over three hundred vertical-critical orbits are given, classified in twenty-one series. Their horizontal stability is also examined and this leads to predictions of where in the range of μ stable three-dimensional periodic orbits may not branch from these basic families.

Journal ArticleDOI
TL;DR: Two male recombination factors, the 31.1 and 23.5 MRF isolated from the same natural population, were tested for the induction of specific deletions and duplications in the regions b and cn of the second chromosome and different results obtained are discussed.
Abstract: 2 male recombination factors, the 31.1 and 23.5 MRF isolated from the same natural population, were tested for the induction of specific deletions and duplications in the regions b and cn of the second chromosome. Genetic and cytological analysis of the double recombinants derived from appropriate crosses of the 23.5/ CyL 4 and 31.1/ CyL 4 strains with the dp b cn bw; ve revealed the following differences between the 2 MRFs. 1. (1) The 23.5 MRF induced (a) higher frequencies of double “putative” recombinants, which often appeared in large clusters, (b) large clusters of single recombinants and (c) cases where the wild-type and sometimes the dp b cn bw phenotype were not produced among the F 2 –F 10 progeny. Such cases were never found with 31.1 MRF. 2. (2) The b and cn recombinants carried deletions whereas the reciprocal dp cn bw and dp b bw had duplications of the corresponding regions. Each cluster carried an identical deletion or duplication. 3. (3) The breakpoints of the 22 cn deletions detected were distributed in the polytene region 42E–44C. On the basis of the cn deletions, we mapped the cn and so loci to polytene intervals 43E6–16 and 42E3.4–43C5.6, respectively. Hypotheses explaining the different results obtained by the 2 factors are discussed.

Journal ArticleDOI
TL;DR: In this paper, the mutual diffusion coefficients of two gases A and B can be determined in an empty gas chromatographic column by letting component B enter at an intermediate position of the column and continuously flow through a part only of it, as a carrier gas.
Abstract: Mutual diffusion coefficients of two gases A and B can be determined in an empty gas chromatographic column by letting component B enter at an intermediate position of the column and continuously flow through a part only of it, as a carrier gas. The other component A is injected in a small amount instantaneously at the closed end of the column with the detector placed at the other end. By repeatedly stopping and then restoring after a short time the flow of B, narrow extra peaks are produced on the chromatographic elution curve, owing to diffusion of A into B. An equation is derived giving the area under the curve of each stop-peak as a function of time of the corresponding stop. Plotting the experimental data according to this equation permits the determination of the diffusion coefficient of A into B. Some results obtained by this method show negligible variations with changes in the experimental parameters.

Journal ArticleDOI
TL;DR: In order to discover new useful steroids in which the cyclopentanoperhydrophenanthrene system is condensed with various heterocyclic rings, many new compounds are continually being synthesized and tested for physiological action as discussed by the authors.

Journal ArticleDOI
TL;DR: SDS gel electrophoresis has revealed, that two polypeptides α and β, are responsible for the formation of the two major bands found during native gel elect phytochemical analysis of Dacus oleae.

Journal ArticleDOI
TL;DR: It is shown that out of the nine electrophoretic zones of activity observed on polyacrylamide gel using crude extract, only two belong to LDH, as revealed by purified enzyme preparations, and purified LDH exhibits activity in two bands on starch gel, which appear in different positions as compared with those of ADH.
Abstract: An electrophoretic variant in the LDH (l-lactate:NAD oxidoreductase, E.C.1.1.1.27) of Drosophila melanogaster was observed on starch (or polyacrylamide) gels. This variant was found to exhibit an identical isozymic pattern (three isozymes with a decreasing staining density) on starch gel and map position as the Adh locus. On the other hand, anodal polyacrylamide gel electrophoresis in crude extracts has shown LDH to consist of nine bands and ADH of four bands. We have shown that ADH (Alcohol:NAD oxidoreductase, E.C.1.1.1.1) also oxidizes l(+)-lactate or d(−)-lactate with the NAD, while LDH oxidizes ethanol. By using various genetic and biochemical techniques, we have shown that the observed Ldh electrophoretic variant was not a real one and could be attributed to the presence of ADH. We have called this phenomenon “pseudopolymorphism,” and the problem of enzyme specificity has been examined. The appearance of a band in an assay using lactic acid as a substrate is not sufficient evidence for the presence of LDH. Hence, caution is called for before characterizing an electrophoretic band on a gel as being equivalent to the presence of a genetic locus. Out of the nine electrophoretic zones of activity observed on polyacrylamide gel (or out of the six previously observed) using crude extract, only two (one major and one minor) belong to LDH, as revealed by purified enzyme preparations. Furthermore, purified LDH exhibits activity in two bands on starch gel (out of three observed in crude extracts), which appear in different positions as compared with those of ADH. Finally, one band which responds to the presence of d(−)-lactate but not to l(+)-lactate has been revealed.