Showing papers by "University of Patras published in 1977"
TL;DR: In this article, the linear wear rate and the surface roughness change with the initial roughness of a bearing during running-in, and the model offers a quantitative explanation of previous observations on the importance of the initial surface rougheness.
40 citations
TL;DR: An argument was provided that environmental temperature was operating as a selective agent in demanding the relative frequencies of the two alleles at this metabolically important locus, and additional evidence is presented to support this proposal based on an evolutionary pattern of coincidence.
Abstract: THE molecular basis for the maintenance of a gene–enzyme polymorphism in natural populations of Drosophila melanogaster has been reported1. The locus under analysis codes for the subunit of α-glycerophosphate dehydrogenase, (α-GDH; E.C. 1.1.1.8) a homodimeric enzyme: the primary function of this enzyme in adult muscle is to provide metabolic energy during flight2–7, and these alleles showed both spatial and temporal variations in frequency. A latitudinal cline was identified, in which the frequency of the α-GDHS allele decreases southwards along the eastern US coast8. The α-GDHS allele was also found to increase in frequency during cooler months in several New England populations6. We evaluated several biochemical parameters using partially purified enzyme from the three common genotypes and uncovered temperature-dependent differences in Km, specific activity, and reaction rate constancy1. Based on the population and biochemical data an argument was provided that environmental temperature was operating as a selective agent in demanding the relative frequencies of the two alleles at this metabolically important locus. We present here additional evidence to support this proposal, based on an evolutionary pattern of coincidence.
34 citations
TL;DR: A second chromosome of Drosophila melanogaster (symbol 31.1) isolated from a natural population of North-Western Peloponnesus (at a distance of 8 km from the city of Patras) was found to induce recombination in heterozygous males, both in the second and third chromosomes as discussed by the authors.
Abstract: A second chromosome of Drosophila melanogaster (symbol 31.1) isolated from a natural population of North-Western Peloponnesus (at a distance of 8 km from the city of Patras) was found to induce recombination in heterozygous males, both in the second and third chromosomes. The present study also revealed the following points. (1) The phenomenon is temperature-sensitive with higher male recombination at 29 °C than at 25 or 15 °C. (2) The temperature-sensitive period is during the larval stage where premeiotic divisions of germ cells take place. (3) Suppression of male recombination in both the second and third chromosomes occurred when 31.1/CyL4 females were used in the matings, and (4) the suppression of male recombination is caused by a cytoplasmic factor of the CyL4/Pm stock.
33 citations
TL;DR: In this paper, the thermomechanical spectra of a series of elastoplastic polyether-ester copolymers were determined at 110 Hz and between −120°C and 200°C at five compositions.
Abstract: The thermomechanical spectra of a series of elastoplastic polyether–ester copolymers were determined at 110 Hz and between −120°C and 200°C at five compositions. Emphasis was given to samples containing an increasing amount of poly(tetramethylene terephthalate) constituting the hard segment in these copolymers. The effects of thermal history, uniaxial drawing, and solvent absorption were examined. Specimens cut from injection-molded slabs were also included in the study. Thermal and mechanical treatment had an important effect on the dynamic mechanical properties. The relaxation spectra do not indicate distinct phase separation, but rather a structure of closely interacting hard and soft segments. The molecular origin of the various relaxations was characterized, and it is shown that as the amount of the hard component increases, features in the relaxation spectrum characteristic of poly(tetramethylene terephthalate) become prominent.
29 citations
TL;DR: Dormant barley seeds contain at least 7 acid phosphatases and this number increases to more than 25 when the seeds are allowed to germinate for 120hr, which is insensitive to actinomycin-D.
21 citations
15 citations
TL;DR: In this paper, the ability of homogeneously aligned nematics with a positive dielectric anisotropy to exhibit Williams Domain as a threshold effect is numerically investigated.
Abstract: The ability of homogeneously aligned nematics with a positive dielectric anisotropy to exhibit Williams Domain as a threshold effect is numerically investigated. A simplified two-dimensional model which has, already, given satisfactory results in the negative dielectric anisotropy case is used. The frequency dependence of the threshold fields obtained for materials with small dielectric anisotropies is in satisfactory qualitative agreement with the known experiments. The frequency dependence of the threshold spatial wavenumbers is calculated. In accordance with earlier work, a positive dielectric anisotropy nematic which normally does not exhibit Williams Domains, does so under the action of a stabilizing magnetic field. This effect is confirmed and the frequency dependence of the threshold fields as well as the assoiated threshold spatial wavenumbers, for various values of the stabilizing field, are calculated. In addition, the model predicts the existence of a class of positive dielectric aniso...
10 citations
TL;DR: In this article, synthetic routes leading to the preparation of 4-substituted 1,4-benzodiazepine-3,5-diones are described.
10 citations
TL;DR: This paper model a multihierarchical level system which communicates with the environment via a specific pair of hierarchical levels Q and W (Figure 1).
9 citations
TL;DR: In this article, the authors derived from the fundamental Cauchy's first law of continuum mechanics the explicit form of the Eulerian general equation which governs the three-axial generalized rotation about the centre of mass of a self-gravitating deformable finite material continuum, viscolinear (i.e., Newtonian) or not, consisting of compressible fluid of arbitrary viscosity, in an external field of force.
Abstract: The aim of the present investigation has been to derive from the fundamental Cauchy's first law of continuum mechanics the explicit form of the Eulerian general equation which governs the three-axial generalized rotation about the centre of mass of a self-gravitating deformable finite material continuum, viscolinear (i.e., Newtonian) or not, consisting of compressible fluid of arbitrary viscosity, in an external field of force. The generalized rotation is a superposition of the so-called rigid-body (i.e., time dependent only) rotation of the continuum plus a nonrigidbody (i.e., position-time dependent) rotation of its configurations.
8 citations
TL;DR: In this paper, the authors analyzed one-degree-of-freedom, elastoplastic structures using ground motions (both real and calculated) whose elastic response spectra have peaks attributable to site conditions, and they concluded that a building with a period equal to that of a site may be more susceptible to yielding during moderate earthquake, but the larger yielding during a major earthquake is much the same as for a building having a different period.
Abstract: A building with a period equal to that of a site may be more susceptible to yielding during a moderate earthquake, but the larger yielding during a major earthquake is much the same as for a building having a different period. This conclusion results from analyzing one-degree-of-freedom, elastoplastic structures using ground motions (both real and calculated) whose elastic response spectra have peaks attributable to site conditions. Inelastic response spectra for site-modified motions do not show pronounced peaks at the period of the site; rather, they are as “smooth” as inelastic spectra computed from motions unaffected by site conditions. Inelastic spectra for design may be based upon the same ratios of spectral acceleration to peak acceleration and spectral velocity to peak velocity as for normal motions. Thus, the amount by which a site modifies peak acceleration and peak velocity is important, and the period of a site is not significant by itself.
TL;DR: In this article, the authors presented the results of the application of the model used in Ref. 1 to the case where the exciting electric field is a sinusoidal one, using the physical constants of the room temperature nematic MBBA,2-5 was in satisfactorily good agreement with experiments.
Abstract: In a recent paper1 a method has been presented for the numerical computation of the electrohydrodynamic (EHD) instability limits and the corresponding director spatial wavenumbers (DSW) of a homogeneously aligned nematic cell, under the action of square-pulse electric field. The results obtained, using the physical constants of the room temperature nematic MBBA,2-5 was in satisfactorily good agreement with experiments. The aim of this note is to present the results of the application of the model used in Ref. 1 to the case where the exciting electric field is a sinusoidal one. Such an application has already been published for the one-dimensional model,6-8 as well as, for the two-dimensional one.9 It is well known, however, that the calculations based on the one-dimensional model do not permit the explicit calculation of the DSW at the conduction mode (CM) thresholds.10 On the other hand, the calculations of Ref. 9 are restricted to the CM of EHD instability under the, only approximately true, as...
TL;DR: A number of partly known families of symmetric three-dimensional periodic orbits of the restricted three-body (μ=0.4) problem are numerically continued in both ends until they terminate with orbits in the plane of motion of the primaries.
Abstract: A number of partly known families of symmetric three-dimensional periodic orbits of the restricted three-body (μ=0.4) problem are numerically continued in both ends until they terminate with orbits in the plane of motion of the primaries. The families of plane symmetric periodic orbits from which they bifurcate are identified and many orbit illustrations are given.
TL;DR: In this article, a complete family of asymmetric periodic oscillations of a charged particle in the meridian plane of a magnetic dipole is presented, which consists of many stable and unstable segments.
Abstract: A complete family of asymmetric periodic oscillations of a charged particle in the meridian plane of a magnetic dipole is presented. It begins at a bifurcation with the principal family of symmetric periodic oscillations and terminates in a flat equatorial oscillation. It consists of many stable and unstable segments.
TL;DR: In this article, the dispersion relation for density waves propagating at an arbitrary angle is derived for a two-arm galaxy and the existence of a resonance which can be stable, neutral or unstable.
Abstract: The dispersion relation has been derived for density waves propagating at an arbitrary angle. The analysis has shown the existence of a resonance which for a two-arm galaxy can be stable, neutral or unstable as\(\omega /2\Omega \tfrac{ }2\), respectively.
TL;DR: In this article, a new algebraic method for solving the Boltzmann equation for the transport equation of neutrons was proposed, which among others gives the real and complex sets of eigenvalues.
TL;DR: In this paper, the free dynamic response of a highly nonlinear free-piston engine and its stability was studied and tabulated for a wide range of parameter constellation, and the design curves given in the paper can assist the designer for the proper selection of the starting system and the proper range of speeds for stable operation.
TL;DR: In this paper, the Peierls-Luttinger theorem for a Bloch electron in a uniform electric and magnetic field was generalized by using an appropriate exponential transformation, which was shown to generalize to the case of a single electron.
TL;DR: In this paper, the dispersion relation for a galaxy without the assumption that the centrifugal force is balanced by the gravitational force has been found for ω = 2Ω (Ω=angular velocity of the Galaxy).
Abstract: The dispersion relation has been found for a galaxy, without the assumption that the centrifugal force is balanced by the gravitational force. It has been shown that such a system (1) can be gravitationally unstable under appropriate conditions, and (2) that there is no resonance at ω=2Ω (Ω=angular velocity of the Galaxy).
TL;DR: A passive diffusion method is described and is compared with other methods for the application of chemicals in early chick embryos in ovo.
Abstract: A passive diffusion method is described and is compared with other methods for the application of chemicals in early chick embryos in ovo.
TL;DR: In this article, a general approach to the design/simulation of optimal distributed-parameter controllers and filters based on a combination of Galerkin and Walsh function expansions is presented.
TL;DR: In this article, the authors considered the presence of a transverse magnetic field near a harmonically oscillating limiting surface (e.g., of a star) and showed that two distinct boundary layers exist and tend to coalesce into a single layer when the magnetic field parameter approaches zero.
Abstract: Unsteady hydromagnetic flow near a harmonically oscillating limiting surface (e.g., of a star) is considered in presence of a transverse magnetic field. Exact solutions, for a periodic boundary layer without a ‘mean steady flow’,are obtained when the magnetic Prandtl number is unity and there is a normal velocity of injection imposed at the wall. The results are also presented for the case when the wall is subjected to a normal velocity of suction instead of injection. It is observed that two distinct boundary (or hydromagnetic boundary) layers exist and tend to coalesce into a single layer when the magnetic field parameter approaches zero. The thicknesses of these boundary layers are significantly affected by the injection/suction velocity and the applied magnetic field.
TL;DR: In this article, a method permitting to find the solution of the Liouville equation of quantum statistical mechanics was developed permitting to obtain the Canonical Distribution of Canonical distributions of the Lipschitz distribution.
TL;DR: In this article, the area under the curve of the stop-peaks is derived for non-equilibrium stopped-flow gas chromatography, where adsorption-desorption is assumed to take place at two kinds of reactive sites.
TL;DR: In this article, a unified approach to input-output decoupling of linear multivariate control systems described by dynamic operator equations is presented, which includes as special cases all linear decoupled results presently known and to cover some new cases not previously studied.
Abstract: A unified approach to input-output decoupling of linear multivariate control systems described by dynamic operator equations is presented. The motivation of the approach is to include as special cases all linear decoupling results presently known and to cover some new cases not previously studied. The generality of the results is due to three facts: first to the inclusion of a direct input-output effect in the system model, secondly to the utilization of operator theory concepts and thirdly to the treatment of the case where the decoupling matrix operator B* is singular by means of dynamic compensation. Several examples illustrate the generality of the present theory and give some now situations whore input-output decoupling is of importance
TL;DR: In this paper, the behaviour of a magnetic line has been studied under continuous injection of plasma and the existence of three zones of possible concentration has been shown under increasing density, for values greater than a critical value, withD suitably defined, one zone disappears, whilst the other two degenerate into one.
Abstract: The behaviour of a magnetic line has been studied under continuous injection of plasma. Under increasing density the existence of three zones of possible concentration has been shown. For values greater than a critical valueD=0, withD suitably defined, one zone disappears, whilst the other two degenerate into one.