Showing papers by "University of Palermo published in 1983"
TL;DR: It appears that the concept of the piscine heart as a typical "venous" type is an oversimplified generalization, at least on morphological grounds, in relation to the phylogenetic and functional context of the fish heart.
Abstract: The typical fish heart has a spongy trabeculated ventricular myocardium (spongiosa) supplied by the venous blood of the intertrabecular spaces (lacunae); hence it is called a "venous heart." However, in some fishes a more complex ventricular muscle is found (mixed type), in which the spongiosa is covered by an outer layer of densely arranged myocardial bundles (compacta). The compacta receives oxygenated blood from the coronary vessels. The objective of this study was to investigate relations between myoarchitecture and blood supply with an emphasis on the hitherto unexplored, putative vascular connections between the arterial and the lacunary circuits. Using histological methods combined with vascular cast techniques and India ink injections, it was possible to define four different types of ventricular myocardium and its microvasculature. In some of them an intramural network arises from the subepicardial arterial system supplying the compacta and also is distributed to the spongiosa. Extensive arterio-luminal vessels connect this coronary bed with the lacunary circuit of the spongiosa, so realizing the first evolutionary step of the Thebesian system. The highest development of these connections is found in some very active pelagic fishes. The functional morphology of these vascular patterns is discussed in relation to the phylogenetic and functional context of the fish heart. It appears that the concept of the piscine heart as a typical "venous" type is an oversimplified generalization, at least on morphological grounds.
125 citations
TL;DR: In this paper, a physical interpretation of the energy shift of the ground state of a hydrogen atom is presented, which emphasizes the role of the field due to the cloud of virtual photons which surround the atom.
69 citations
TL;DR: In this paper, a parallel-wall configuration was used for photocatalytic ammonia synthesis in a fluidized reactor of parallel wall configuration by irradiating iron-doped titanium dioxide with near ultraviolet light.
63 citations
TL;DR: The relationship between heart ventricle weight and body weight has been determined for three species of Antarctic fish with respiratory pigments, and some unusual characteristics of these mitochondria are reported and discussed in relation to the unique constraints characterizing this type of heart.
50 citations
TL;DR: In this paper, the 2-pyridyl group of strong acids HX and HClO4 has been shown to have a carbene-like limiting structure in the electronic configuration of a new type of ligand.
48 citations
TL;DR: In this paper, the reaction of allyl iodide was studied at the surface of four tungsten oxides and molybdenum trioxide, and it was concluded that the transformation of a corner-linked into an edge-linked arrangement of metal-oxygen octahedra provides a facile route for insertion of oxygen into a hydrocarbon molecule.
43 citations
TL;DR: In this paper, a simple calorimetric method is proposed to evaluate at the same time all thermodynamic functions (Δ G ° t, Δ H ° t, and Δ S ° t ) for the transfer process of a solute from the solvent to the micelles.
39 citations
TL;DR: The oxygen isotope composition of carbonate from the outermost portions of Patella coerulea, Monodonta turbinata and M. articulata shells has been measured from April 1979 to July 1981, with an interval during the summer of 1980, and correlated with the ambient temperature as mentioned in this paper.
31 citations
TL;DR: A new and versatile technique is described for the study of the structure and formation of the HbS aggregates, that should be widely applicable to gel systems generally and should be understood if a rational strategy is to be developed for pharmacological intervention.
Abstract: The aggregation of sickle-cell haemoglobin (HbS) is one of the most physiologically important and widely studied macromolecular gelation processes. Both the thermodynamics and kinetics of the process are important in determining the pathological consequences of deoxygenation of the red cells (and both must be understood if a rational strategy is to be developed for pharmacological intervention). We describe here a new and versatile technique for the study of the structure and formation of the HbS aggregates, that should be widely applicable to gel systems generally. We use laser autocorrelation spectroscopy to observe the diffusion of monodisperse polystyrene latex spheres in the interstices of the gel.
30 citations
TL;DR: In this paper, a measurement system is described which allows the determination of the complex permittivity of high-loss liquids at millimeter waves, using a waveguide interferometer whose unknown arm embodies a liquid holder irradiated by an openended rectangular waveguide.
Abstract: A measurement system is described which allows the determination of the complex permittivity of high-loss liquids at millimeter waves. Basically, the setup consists of a waveguide interferometer whose unknown arm embodies a liquid holder irradiated by an open-ended rectangular waveguide. The sample thickness is varied by means of a piston driven by a micrometer screw. The bridge output then is read as a function of the liquid thickness. Best fitting between experimental and computed data through a suitable model of the system enables the permittivity to be determined. The system can operate, with high sensitivity, over the whole frequency range of the dominant mode propagating in the waveguide setup employed. System performance is described through a set of experimental results obtained on ethanol, methanol, and pure water at 20° C and 70 GHz.
28 citations
TL;DR: The ability of uridine to interact competitively with GABA binding sites suggests a possible mechanism of action of this anticonvulsant agent, so including it among those compounds characterized by a GABAergic agonist activity is included.
Abstract: The effect of uridine, a postulated anticonvulsant agent, on GABA receptors has been investigated. Uridine inhibits [3H]GABA binding to rat cerebellar buffer-washed membranes. Pretreatment of the membranes with Triton X-100 increases the effect of uridine on GABA-binding. The Scatchard analysis reveals that both high and low affinities of GABA for its receptors are affected by 1 mM uridine, while the apparent number of binding sites remains unchanged. The ability of uridine to interact competitively with GABA binding sites, also examined by the Lineweaver-Burk analysis, suggests a possible mechanism of action of this anticonvulsant agent, so including it among those compounds characterized by a GABAergic agonist activity.
TL;DR: In this paper, the densities, heat capacities, and dilution enthalpies of n-pentanol+2-methyl-2-butanol mixtures have been measured, in many cases as a function of temperature.
Abstract: The densities, heat capacities, and dilution enthalpies ofn-pentanol+2-methyl-2-butanol mixtures have been measured, in many cases as a function of temperature, over the complete mole fraction range. Excesses thermodynamic properties, apparent and partial molar heat capacities, volumes and expansibilities were derived. The concentration and temperature dependences of these functions are discussed in terms of the variations of the structure of the system caused by the participation of the two alcohol molecules (with quite different steric hindrance of the alkyl chain around the-OH group) in the dynamic intermolecular association process through hydrogen bonding.
TL;DR: The structure of chromatin of rat hepatocyte nuclei has been studied and rosette-like structures having an electron-dense core and numerous loops are isolated from nuclei with diffuse chromatin.
TL;DR: In this paper, photo-induced growth of ZnS on CdS has been studied using amorphous (thin film) and single-crystal substrates, with a growth rate of 2000 A/min.
Abstract: Photo-induced growth of ZnS on CdS has been studied using amorphous (thin film) and single-crystal substrates. The effect has been found to occur for light of wavelength shorter than the CdS absorption edge; a maximum light-induced thickness enhancement of 700 A has been obtained for the ZnS film, with a growth rate of 2000 A/min. The light-induced growth, with its observed “memory” of several minutes is consistent with photo-desorption of an adlayer.
TL;DR: In this article, the transmission of light through an irradiated fluidised bed with vertical flat walls containing catalytic particles has been experimentally studied, and the amount of light transmitted through the reactor was measured at different levels by a photocell.
TL;DR: The conclusion of the present experiments is that sea urchin embryonic cells become responsive to heat shock and produce heat shock proteins even in the absence of cell interactions.
TL;DR: In this article, the rheological behavior of three types of HDPE/LDPE blends at several compositions (various weight percentages of LDPE) was studied with the aid of a capillary rheometer and three different capillaries.
Abstract: The rheological behaviour of three types of HDPE/LDPE blends at several compositions (various weight percentages of LDPE) has been studied with the aid of a capillary rheometer and three different capillaries.
TL;DR: In this article, the mechanism of catalytic hydrogenation of conjugated trienes in the presence of 1.5-COD was investigated under mild conditions of temperature (20 °C) and hydrogen pressure (1 atm).
TL;DR: A minimum spanning forest method is described which finds cluster patterns in a random graph of points and a uniformity test suitable for low statistics data sets is proposed.
TL;DR: In this paper, low density polyethylene-isotactic polypropylene blends have been irradiated in the dose range 0-150 Mrad and structural modifications have been investigated by means of solubility, calorimetric and density measurements.
TL;DR: In this article, a new 19-nor-neo-clerodane diterpenoid, 6-epiteucrin A, has been isolated from the aerial part of Teucrium chamaedrys.
TL;DR: In this paper, the effect of aluminum hydroxide on the dielectric properties of epoxy resins has been studied in a wide frequency and temperature range, and an interfacial polarization effect known as the Maxwell-Wagner-Sillars polarization is evidenced for the filled resins.
Abstract: The effect of aluminum hydroxide upon the dielectric properties of an epoxy resin has been studied in a wide frequency and temperature range. An interfacial polarization effect, known as the Maxwell–Wagner–Sillars polarization is evidenced for the filled resin, which shows a higher permittivity, a higher dielectric loss, and a β transition with a larger relaxation time. The glass transition temperature is, on the contrary, mostly unaffected by the presence of the filler.
TL;DR: In this paper, a melt spinning and viscosity study of two semi-lexible homopolymers containing both rigid and flexible segments in the repeating unit was performed. And the results showed that these types of polymers do not possess adequate chain extension to develop ultra-high-modulus properties.
Abstract: We report a melt spinning and viscosity study of two semiflexible homopolyesters containing both rigid and flexible segments in the repeating unit Single filaments of the polyesters formed from 4,4′-diacetoxybiphenyl and azelaic acid (PB7) and sebacic acid (PB8), and from 4′-hydroxyphenyl-4-hydroxycinnamate and azelaic acid (C7), were spun at temperatures between 205 and 255°C The temperature dependence of the Newtonian melt viscosity of PB7 and C7 was investigated, and a range of molecular weights was studied for PB7 The spinning parameters, fiber characteristics, and viscosity-temperature behavior are related to the type of mesophase formed The mechanical properties of fibers spun from both the nematic and smectic phases of these semiflexible chain polymers were poor Increasing the polymer molecular weight or extrusion rate only afforded a modest improvement in fiber properties Most polymers could not be spun at temperatures corresponding to the existence of the single mesophase Hence the low viscosity typical of the nematic mesophase is not necessarily an advantage in fiber formation from the melt It appears from these results that this type of polyester does not possess adequate chain extension to develop ultrahigh-modulus properties The director, which describes the local orientation of molecules within the mesophase, may undergo more frequent variations than is the case for rigid chain polyesters Mechanisms relevant to flexible polymers may contribute to the development of orientation for this class of nematogenic melts
TL;DR: The topologic stereodynamic structures of connectivity pathways in the solvent, as modified by interaction with solutes, acquire a specific thermodynamics and biological significance, and the problem of thermodynamic and functional stability of biomolecules is seen in its full pertinent phase space.
Abstract: Thermodynamic interpretation of experiments with isotopically perturbed solvent supports the view that solvent stereodynamics is directly relevant to thermodynamic stability of biomolecules. According with the current understanding of the structure of the aqueous solvent, in any stereodynamic configuration of the latter, connectivity pathways are identifiable for their topologic and order properties. Perturbing the solvent by isotopic substitution or, e.g., by addition of co-solvents, can therefore be viewed as reinforcing or otherwise perturbing these topologic structures. This microscopic model readily visualizes thermodynamic interpretation. In conclusion, the topologic stereodynamic structures of connectivity pathways in the solvent, as modified by interaction with solutes, acquire a specific thermodynamic and biological significance, and the problem of thermodynamic and functional stability of biomolecules is seen in its full pertinent phase space.
TL;DR: In this paper, the Si Al ratio of the starting material was of special importance in that zeolites formed with Si Al ratios similar to or smaller than that of the parent material.
TL;DR: The pentacyclic triterpene acids ursolic acid, oleanolic acid and micromeric acid have been isolated from several Salvia and Teucrium species as discussed by the authors.
TL;DR: Isotopic and chemical investigations of Lake Specchio di Venere on the island of Pantelleria (Italy) have been carried out in order to investigate the relationships existing between the lake water and the thermal springs feeding the lake.
TL;DR: The effect of a single 20 mg aspirin dose on serum TXB2, was of much longer duration than its inhibitory effect on PGI2 synthesis during whole blood clotting.
Abstract: The effects of two low doses of aspirin (20 mg and 100 mg) on prostacyclin and thromboxane formation during whole blood clotting were studied in 8 healthy volunteers. A single 100 mg aspirin dose caused more than 90% reduction of both serum TXB2 and 6-keto-PGF1 alpha; a single 20 mg dose of aspirin inhibited serum TXB2 more than 6-keto-PGF1 alpha but effects on these two products could not be completely dissociated. However, the effect of a single 20 mg aspirin dose on serum TXB2, was of much longer duration than its inhibitory effect on PGI2 synthesis during whole blood clotting.
TL;DR: In this article, the synthesis of 1,10-phenanthroline with SbX 3 (X = F, Cl, Br) and PhSbI 2 is described.