Showing papers by "University of Patras published in 1983"
TL;DR: In this paper, a de Laval rotor with an open crack is investigated by way of application of the theory of shafts with dissimilar moments of inertia, and analytical solutions are obtained for the closing crack under the assumption of large static deflections, a situation common in turbomachinery.
268 citations
TL;DR: In this article, a generalized geometric distribution is introduced and briefly studied, and sufficient conditions are presented under which we can derive the limiting distribution of Yr - kr as r → ∞.
206 citations
TL;DR: In this paper, a general flexibility matrix is developed which expresses the local flexibility of a beam of rectangular cross section with a single edge crack, and the dominant term in this matrix is used to study the stability of the cracked column to follower and vertical loads.
120 citations
TL;DR: Activity differences between light and darkness are maximized when glycerol (25% v/v) is included in the extraction medium and in the absence of mercaptoethanol, suggesting post-translational regulation.
Abstract: Photoactivation of phosphoenolpyruvate carboxylase was found to occur in several, though not all, C 4 species examined; Salsola soda L. was used for a detailed study of this effect of light. Activity differences between light and darkness are maximized when glycerol (25% v/v) is included in the extraction medium and in the absence of mercaptoethanol. In plants grown in the growth chamber, the night-form of the enzyme, in addition to low activity, shows a positive cooperativity (with phosphoenolpyruvate), which is gradually abolished by light of increasing intensities. This allosteric behavior is absent in plants adapted to a high light environment. Activation and deactivation, under light and darkness respectively, are quite fast, suggesting post-translational regulation. The photoactivation appears to depend on photosynthetic electron flow, since it is saturated at high photon fluxes (around 1000 microeinsteins per square meter per second) and inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea.
75 citations
TL;DR: Four major hemolymph polypeptides (ceratitins) with molecular weights between 8.1 X 10(4) and 8.7 X 10 (4) daltons have been identified in the fat body of late Ceratitis capitata larvae and comparison of the biosynthetic patterns obtained suggests a linear relationship between messenger concentration and protein synthesis.
49 citations
TL;DR: In this article, the infrared spectra of aluminium chloride vapour (AI2CI6 and AIC13) including Aii5C16 and Ali7Clti at 473-843 K were measured with an evacuable Fourier transform spectrometer by transmission and emission techniques.
Abstract: The infrared spectra of aluminium chloride vapour (AI2CI6 and AIC13) including Aii5C16 and Ali7Clti at 473-843 K were measured in the region 700-50 cm-' with an evacuable Fourier transform spectrometer by transmission and emission techniques. Evacuable cells of nickel were employed having windows of type IIa diamond and sealed with gold O-rings. Raman spectra of AI,C16 vapour at cu 500 K and of AIC13 at 1075 K with pressures from 0.3 to 10 atm were recorded, polarization measurements were carried out and additional spectra of the 35CI and 37CI compounds were obtained. The dimer spectra were interpreted in terms of DZh symmetry. All the nine Raman-active and seven of the infrared-active dimer fundamentals were assigned. The IR active mode ulo(B1.), expected below 40 cm-', and the inactive mode u,(A.) were left unassigned. The monomer spectra were interpreted in terms of Dfh symmetry and all four fundamentals were assigned. A dimer force field, involving 12 independent force constants, was derived. The calculated frequencies were fitted with a least-squares programme to 30 observed fundamentals of AI:'C1, and AlFCl6 and 14 additional isotopic shifts transferred from previous matrix isolation spectra. A complete force field for the monomer was derived, using the four observed fundamentals and seven isotopic shifts transferred from previously reported matrix isolation spectra.
47 citations
TL;DR: In this paper, a sharp crossover was observed in the variation of the reduced viscosity ηsp/c as a function of the concentration c for mixtures of polystyrene and poly(methylmethacrylate) in benzene at 20°C.
Abstract: A very sharp crossover is observed in the variation of the reduced viscosity ηsp/c as a function of the concentration c for mixtures of 1:1 by weight mixtures of polystyrene and poly(methylmethacrylate) in benzene at 20°C and a 1:1 by weight mixture of poly(ethylene glycol) and polystyrene in benzene at 20°C. The crossover is attributed to the critical to the concentration of the two respective polymers in the solution and its sharpness is due to the incompatibility between the two different polymers.
44 citations
TL;DR: It is concluded that the character studied is quantitative, responds to selection pressure and is transmitted through the maternal cytoplasm, while nuclear genes modify its expression.
Abstract: Non-Mendelian inheritance was revealed for the "heat-sensitivity" character of the poikilothermic insect Drosophila melanogaster. Genetic analyses were performed on heat-sensitive (S, S1) strains, derived through indirect selection, and on stocks constructed through extensive chromosomal and cytoplasmic substitutions between strains obtained from two replicate cage populations. The populations were kept for about 7 years under different temperatures (14°-25°) and exhibited different survival. We conclude that the character studied is quantitative, responds to selection pressure and is transmitted through the maternal cytoplasm, while nuclear genes modify its expression.
37 citations
TL;DR: Three new modified steroidal alkylating agents, 3β-hydroxy-13α-amino-13,17-seco-5α-androstan-17-oic- 13, 17-lactam-p-bis(2-chloroethyl)aminophenylacetate, are active in treatment of L1210 and P388 leukemias and certain conclusions are drawn regarding structure-activity relationships.
Abstract: Three new modified steroidal alkylating agents, 3β-hydroxy-13α-amino-13,17-seco-5α-androstan-17-oic-13,17-lactam-p-bis(2-chloroethyl)aminophenylacetate, 3β-hydroxy-13α-amino-13,17-seco-5α-androstan-17-oic-13,17-lactam-p-bis-(2-chloroethyl)aminophenylbutyrate, and 17β-hydroxy-3-aza-A-homo-4α-androsten-4-one-p-N,N-bis(2-chloroethyl)-aminophenylacetate are active in treatment of L1210 and P388 leukemias. A stereoisomer of the first compound, 3α-hydroxy-13α-amino-13,17-seco-5α-androstan-17-oic-13, 17-lactam-p-bis(2-chloroethyl)aminophenylacetate, was tested in L1210 leukemia. This stereoisomer, in which the alkylating agent is linked to the modified steroid in the axial position, is active only at much higher doses in L1210 leukemia. The results of testing these compounds and previous results from similar compounds allow certain conclusions to be drawn regarding structure-activity relationships. The presence of the lactam moiety is the major structural feature that confers activity in the murine leukemias. The steric arrangement of the alkylating moiety at position 3 and the hydrogen atom at position 5 influence toxicity and antileukemic activity.
36 citations
TL;DR: Bacteremic pneumonia due to aerobic gram-negative bacilli was diagnosed in 27 patients during a 20-month period and worsened prognosis of patients with pneumonia was unrelated to the species of infecting organisms or the underlying conditions or disease.
Abstract: • Bacteremic pneumonia due to aerobic gram-negative bacilli was diagnosed in 27 patients during a 20-month period. The mortality was high (81.5%) among these elderly patients (mean age, 61.2 years) with serious underlying disease, in spite of amikacin sulfate therapy that was appropriate as determined by susceptibility testing. Bacteremic pneumonia accounted for 14.1% of patients with gram-negative bacteremia but was responsible for 39.4% of the deaths in the total group of 191 patients. The worsened prognosis of patients with pneumonia was unrelated to the species of infecting organisms or the underlying conditions or disease. ( Arch Intern Med 1983;143:2147-2149)
36 citations
TL;DR: The polysaccharides of cranical cartilage were isolated by ethanol precipitation after papain digestion and beta-elimination procedures and were fractionated chromatographically on CPC-cellulose and contained small amounts of hyaluronic acid, which, however, co-eluted with the chondroitin sulphate from the CPC-cells.
TL;DR: The glycosaminoglycans thus prepared consisted only of chondroitin-4-sulfate, chond Detroitin-6-solfate, and small amounts of highly hybridized dermatan sulfate, while the experiments failed to demonstrate even trace amounts of keratan sulfates, hyaluronic acid or heparan sulfates.
Abstract: Puppy dentine was prepared using ultracentrifugation of tooth powder in organic density gradients. The glycosaminoglycans of the obtained tissue fraction were prepared after papain digestion andβ-elimination, using preparative chromatography on DEAE-cellulose and CPC-cellulose. These polysaccharide fractions were analyzed using highly sensitive HPLC procedures. One such HPLC procedure allowed hyaluronic acid to be determined in less than microgram amounts.
TL;DR: In this paper, a singular integral equation (with a kernel with a logarithmic singularity) was proposed for the crack problem inside an elastic medium under plane or antiplane conditions.
Abstract: A new singular integral equation (with a kernel with a logarithmic singularity) is proposed for the crack problem inside an elastic medium under plane or antiplane conditions. In this equation the integral is considered in the sense of a finite-part integral of Hadamard because the unknown function presents singularities of order −3/2 at the crack tips. The Galerkin and the collocation methods are proposed for the numerical solution of this equation and the determination of the values of the stress intensity factors at the crack tips and numerical results are presented. Finally, the advantages of this equation are also considered.
TL;DR: In this article, the temperature dependence of mutual diffusion coefficients in the binary gas mixtures C 2 H 6 + He, C 2H 4 + He and C 3 H 4 + N 2 was studied experimentally using the reversed-flow gas chromatography sampling technique.
TL;DR: In this article, Pontryagin's maximum principles are applied to obtain the solution of minimum mass convective fin with variable heat transfer coefficients. But the results are given in a dimensionless form and they are not given in tables or graphs, in order to aid design procedures.
Abstract: Pontryagin's maximum principles are applied to obtain the solution of minimum mass convective fins with variable heat transfer coefficients. It is shown that the volume and the width of the fin are uniquely related to the specified heat transfer rate and the properties of the material. For a power law spatial variation of the heat transfer coefficient, the results are set forth in a dimensionless form and they are given in tables or graphs, in order to aid design procedures. Several properties relating to the optimum volume, base thickness and the width of the fins with the properties of the material are also discussed. The method can also be used to solve problems of minimum mass fins having restricted width, often encountered in practice.
TL;DR: In this article, the reversed-flow method for measurement of gas diffusion coefficients in binary mixtures is extended to simultaneous determination of effective diffusion coefficients for each substance in a multicomponent gas mixture.
Abstract: The reversed-flow method for measurement of gas diffusion coefficients in binary mixtures is now extended to simultaneous determination of effective diffusion coefficients for each substance in a multicomponent gas mixture. The method is applied to six ternary mixtures, each consisting of two gaseous hydrocarbons and H2, He or N2. The results are in agreement with a limiting case of the Stefan-Maxwell equations.
TL;DR: From the individuals examined, six were found to have abnormal karyotypes suggesting chromosomal exchanges, and structural aberrations in which mainly submetacentric and subtelocentric chromosomes are involved have also been described and discussed.
Abstract: The karyotypes of eight wild Greek Paeonia taxa were studied, viz P clusii ssp clusii (2n = 10, 20), P clusii ssp rhodia (2n = 10), P mascula ssp mascula (2n = 20), P mascula ssp hellenica (2n = 20), P mascula ssp icarica (2n = 20), P mascula ssp russi (2n = 10), P peregrina (2n = 20) and P parnassica (2n = 20) P mascula and P clusii have a very similar haploid chromosome complement, x = 5, including three metacentric chromosomes, one submetacentric and one subtelocentric In the chromosome complements of the tetraploid P peregrina and P parnassica the same chromosome types are included but their karyotype differ from those of the former two species by a number of characters The main karyotype differences are concerned with the size differentiation of the chromosomes which in the case of P peregrina has resulted in the diploidization of the tetraploid karyotype
From the individuals examined, six were found to have abnormal karyotypes suggesting chromosomal exchanges These structural aberrations in which mainly submetacentric and subtelocentric chromosomes are involved have also been described and discussed
TL;DR: A survey of the recent advances in the field of distributed parameter systems covers stability, controllability, optimal control, observability, state estimation, identification, sensitivity, computational methods, simulation, and applications.
Abstract: A survey of the recent advances in the field of distributed parameter systems is provided. The results are presented in ten sections, each one covering a distinct topic of the field. These topics are stability, controllability, optimal control, observability, state estimation, identification, sensitivity, computational methods, simulation, and applications.
TL;DR: In this article, the thermochemical storage of energy by the system carbon dioxide, ammonia and ammonium carbamate is studied in detail in particular, the kinetics and the thermodynamics of the reversible reaction is studied and two industrial models for the operation of this system are given.
TL;DR: It is suggested that heat shock proteins could be considered as a major target of temperature-induced selection being another effective molecular mechanism for temperature compensation.
Abstract: 1. 1. It is well known that when various organisms (procaryotes and eucaryotes), cells or tissues receive temperature shock a specific set of new proteins is rapidly synthesized; these proteins are called heat shock proteins (hsps). 2. 2. This heat shock response has been used extensively as a tool for the study of gene structure and regulation in eucaryotes. 3. 3. While heat shock response is similar, in all species examined intra- and inter-specific variability exists with regards to the heat shock genes. 4. 4. It has been shown in a wide variety of organisms (yeasts, insects, mammalian cells) that when they were subject to a mild temperature prior to that which could kill the animals, an enhancement of both the survival rate and the cellular level of hsps occurs, which argues for a fundamental role of these proteins in the acquisition of resistance to heat. 5. 5. Evidence bearing on this physiological significance of the hsps is given by utilizing short- and long-term selected Drosophila strains which exhibit different survival rates (heat sensitive and heat resistant strains). 6. 6. Genetic analysis of the “heat sensitivity” trait revealed that this character is quantitative, responds to temperature selection pressure and is transmitted through the maternal cytoplasm; nuclear genes modify its expression in a minor way. 7. 7. The capacity of heat-induced protein synthesis (in salivary glands or ovaries) is higher for resistant strains, in parallel to their survival, compared with the sensitive ones. 8. 8. Reciprocal hybrids, constructed by sensitive and resistant lines, exhibit survival and heat-induced proteins synthesis patterns which resemble those of their mothers, which quite possibly reflects the involvement of cytoplasmic factor(s) in both the regulation of hsps synthesis and survival. 9. 9. Since selective pressure affects the regulation of the hsps synthesis and the capacity of the animal to survive heat shock, we suggest that these proteins could be considered as a major target of temperature-induced selection being another effective molecular mechanism for temperature compensation.
TL;DR: In this article, the authors examined the possibility of using non-linear comparison systems in the stability analysis of nonlinear dynamical systems and established the stability criteria and estimates of the stability region.
Abstract: This paper examines the possibility of using non-linear comparison systems in the stability analysis of non-linear dynamical systems. Stability criteria and estimates of the stability region of non-linear comparison systems are established. It is shown that the use of non-linear comparison systems may lead to less conservative results than those obtained by linear ones.
Abstract: Fatigue crack growth in resonating members of distributed mass is studied under conditions of dynamic interaction between crack growth and crack load. The crack propagation rate is related to the stress intensity facfor range by way of the well known power law. The depth of the crack determines the local flexibility due to crack which in turn influences the dynamic response of the system under an external force with constant amplitude and frequency. The propagating crack introduces additional flexibility to the continuous system which results in gradual shifting away of the resonance which results in smaller loading of the cracked section. This reduces, in general, the growth rate and brings eventually the system to a value of crack propagation rate below a conventional threshold rate which can be interpreted as dynamic crack arrest. It is important from an engineering standpoint to know the total crack growth at that time which determines the component structural integrity.
TL;DR: The description of the heat shock (HS) system in the insect under investigation has revealed similarities and differences in comparison to that of Drosophila or other taxa, in terms of the electrophoretic distribution on SDS gel of several hsps, the optimum response, the time course of the hsp synthesis etc.
Abstract: 1. 1. Salivary glands from third instar larvae of Ceratitis capitata synthesize a set of at least 8 specific polypeptides in response to heat shock (37°C for 30 min), while the overall protein synthesis is reduced. 2. 2. The main heat shock protein (hsp) was found to have on SDS, an apparent molecular weight 69,000 (69 K) and may correspond to the respective 70 K protein of Drosophila melanogaster . The rest hsps have been named according to their molecular weight as follows: 87, 34, 20, 16, 14, 13 and 12 K. 3. 3. The description of the heat shock (HS) system in the insect under investigation has revealed similarities and differences in comparison to that of Drosophila or other taxa, in terms of the electrophoretic distribution on SDS gel of several hsps, the optimum response, the time course of the hsp synthesis etc. 4. 4. Heat pretreatment at a mild temperature, followed by a heat shock of late third instar larvae resulted in an enhancement of both the survival and the hsp synthesis. Increased hsp synthesis was also observed when salivary glands were exposed to preheating before the heat shock. These observations are discussed in terms of the function l significance of hsps. 5. 5. Based on our data in combination to the information in the literature the selective and evolutionary significance of the heat shock genes is emphasised.
TL;DR: In this paper, an experimental investigation into the shear behaviour of reinforced concrete beams of varying depth, and the way in which they fail in shear, compared to primatic beams, is presented.
TL;DR: The results suggest that ethanol can affect receptor-effector coupling, including the binding of opiate agonists to their receptors, through its membrane-disordering capacity, and that particular systems may react in a relatively specific manner with ethanol.
Abstract: The perturbation of neuronal cell membranes by ethanol may result in specific functional changes through modification of the activity of various membrane-bound proteins. In mouse striatum, adenylate cyclase, a membrane-bound enzyme, is coupled to dopamine, as well as to opiate, receptors. Ethanol stimulates striatal adenylate cyclase activity by modifying the regulatory protein (“G-protein”)-adenylate cyclase interaction to produce an increased amount of activated enzyme. This action is additive with the effects of dopamine on adenylate cyclase. Ethanol also modifies striatal opiate receptor-effector coupling processes. In the presence of ethanol, opiate receptor affinity is altered, and this alteration is modified by GTP, suggesting that ethanol influences the interaction of the opiate receptor complex with the G-protein. Our results suggest that ethanol can affect receptor-effector coupling, including the binding of opiate agonists to their receptors, through its membrane-disordering capacity, and that particular systems may react in a relatively specific manner with ethanol.
TL;DR: In this article, the disodium salts of N-trityl-O-alkyl-hydroxyamino acids were selectively alkylated with alkyl iodides to give N-TRityl O-ALKY-AMINO acids.