Showing papers by "University of Florence published in 1969"
TL;DR: In this paper, the maximum number of degrees of freedom of an image, which is usually derived by a rough application of the sampling theorem, has a precise mathematical meaning, established by applying the theory of prolate spheroidal functions.
Abstract: The maximum number of degrees of freedom of an image, which is usually derived by a rough application of the sampling theorem, has a precise mathematical meaning. This is established by applying the theory of prolate spheroidal functions, as discussed by Slepian and Pollack and other authors. Both coherent and incoherent illumination are considered. The number of degrees of freedom of the image can be substantially different in both cases. A dramatic example is represented by the thin-ring pupil, which is virtually unidimensional in the former case and two dimensional in the latter case.
314 citations
TL;DR: In this article, the question of whether there is a technical meaning, or meanings, of "ideology" which constitute a necessary tool of enquiry for a science of politics is investigated.
Abstract: The word ideology points to a black box. As a philosopher puts it, ideology “signifies at the same time truth and error, universality and particularity, wisdom and ignorance.” Likewise, for the political scientist the term ideology points to a cluster concept, i.e., belongs to the concepts that bracket a variety of complex phenomena about which one tries to generalize; and the growing popularity of the term has been matched, if anything, by its growing obscurity. All in all, one is entitled to wonder whether there is any point in using “ideology” for scholarly purposes. And my specific question will be whether there is a technical meaning, or meanings, of “ideology” which constitute a necessary tool of enquiry for a science of politics.Discussions about ideology generally fall into two broad domains, namely, ideology in knowledge and/or ideology in politics. With respect to the first area of inquiry the question is whether, and to what extent, man's knowledge is ideologically conditioned or distorted. With respect to the second area of enquiry the question is whether ideology is an essential feature of politics and, if so, what does it explain. In the first case “ideology” is contrasted with “truth,” science and valid knowledge in general; whereas in the second case we are not concerned with the truth-value but with the functional value, so to speak, of ideology. In the first sense by saying ideology we actually mean ideological doctrine (and equivalents), whereas in the second sense we ultimately point to an ideological mentality (also called, hereinafter, ideologism).
175 citations
97 citations
01 Jan 1969
96 citations
TL;DR: In this paper, the retention capacity of alginic acid has been investigated and it has been shown that ion exchange is not the only mechanism, but that the influence of the two vicinal hydroxyl groups on the retention capability is also important.
43 citations
TL;DR: The purification procedure consisted of an acid extraction, a precipitation of foreign proteins, a ZnCl 2 precipitation and two subsequent steps on Chromatographic columns of CM-Sephadex C-25.
37 citations
TL;DR: In this article, a vibrational assignment based on the vapour IR rotational band shapes and Raman depolarization data is given, supported by a zero-order frequency calculation, performed by means of a valence force field.
36 citations
TL;DR: Pulse-labelled RNA isolated from nuclei of rat liver and of Yoshida ascites-hepatoma cells forms hybrids with homologous DNA, with a high degree of specificity, which reduces the ability of DNA to hybridize with labelled nuclear RNA.
34 citations
TL;DR: A study on fatty acid composition in cholineand ethanolamine-containing phospholipids of central white matter was carried out in five brains affected by multiple sclerosis and in four controls, finding that in normal tissue, fatty aldehydes have a shorter retention time in respect to their corresponding fatty acids so that they can be identified and calculated independently.
Abstract: RECENT investigations have shown that in multiple sclerosis the white matter lipids undergo changes in their fatty acid composition (BAKER, THOMPSON and ZILKHA, 1963; GERSTL, KAHANKE, SMITH, TAVASTSTJERNA and HAYMAN, 1965). In particular, a study of the total fatty acid composition of the demyelinated tissue in plaques of multiple sclerosis demonstrated a clear decrease of unsaturated C1* fatty acids (AMADUCCI, PAZZAGLI and PETRuzzI, 1965), which are found mostly in the cholineand ethanolamine-containing phospholipids of the white matter (OBRIEN, FILLERUP and MEAD, 1964). It has been suggested that lecithins may play a role in demyelination through the formation of lysocompounds which may derive from lecithins by the loss of the unsaturated Cla fatty acids, presumably from the 2-position of glycerol (THOMPSON, 1966). For these reasons a study on fatty acid composition in cholineand ethanolamine-containing phospholipids of central white matter was carried out in five brains affected by multiple sclerosis and in four controls. The study was carried out using the micromethods for tissue sampling and extraction described by HESS, and THALHEIMER (1965), thin-layer and column chromatography for separation of the different phospholipid fractions (ROUSER, GALLI, LIEBER, BLANK and PRIVEIT, 1964) and gas chromatography for fatty acid and/or aldehydes separation and estimation. Separation of the fatty acids from the fatty aldehydes was not carried out because of the small amount of material. In the experimental conditions used it was found, however, that in normal tissue, fatty aldehydes have a shorter retention time in respect to their corresponding fatty acids so that they can be identified and calculated independently. The exception is the 18: 1 aldehyde which is completely superimposed upon the 18:0 fatty acid in the system used.
31 citations
TL;DR: In this article, the fractional coverage as a function of exposure to oxygen was measured from the intensities of various diffraction beams, and the condensation coefficient was derived at room temperature and above (up to 600 °C).
26 citations
TL;DR: The inhibition of the enzymes by aromatic compounds was investigated and reactivation by PVP and Tween 80 was successfully demonstrated.
TL;DR: There was a global reduction in the number of living microorganisms due to pollution effects, especially yeasts and bacteria, while nitrogen-fixing microorganisms and fungi were less affected.
Abstract: The effect of air pollution on total phyllospheric microflora from two species of the epiphytic neotropical genus Tillandsia (Bromeliaceae) was studied by comparing unpolluted plants living in a forest (Escazu, San Jose) with polluted ones from an urban site of Costa Rica (San Jose city). Dilutions of homogenized leaf samples were plated on media suitable for each microbial group. For each microorganism group, total counts were performed and purified strains of randomly chosen colonies were identified. There was a global reduction in the number of living microorganisms due to pollution effects, especially yeasts and bacteria, while nitrogen-fixing microorganisms and fungi were less affected. Our results showed that the phyllosphere microflora of Tillandsia plants living in a tropical urban environment changes in terms of number and species composition of yeasts and bacteria with respect to plants living in unpolluted environment.
TL;DR: Experimental results suggest that alkaline phosphatase is both a phosphomonoesterase and a pyrophosphatase, and both enzyme activities were affected similarly by cysteine, a noncompetitive inhibitor, and by heating in the absence of substrate.
TL;DR: Alginic acid was tested as an adsorbent in the ion-exchange chromatography of 31 amino acids on thin layers, the eluents being hydrochloric acid, acetic acid, water, potassium nitrate solutions and aqueous organic solvents.
TL;DR: In this article, a modified Lippmann electrometer was used to obtain electrocapillary curves by varying the concentration of aqueous solutions of quinoline, 2-methylquinoline and 4-methyl-quinoline, using 1 N KNO3 as supporting electrolyte.
TL;DR: In this paper, the thin-layer chromatographic and electrophoretic behavior of primary aromatic amines on weak ion exchangers such as alginic acid and carboxymethylcellulose was studied extensively.
TL;DR: In this paper, the transition between low-lying levels of 50 V was studied with the 50 Ti(p, nγ) 50 V reaction and the multipolarities of transitions and spins of levels were deduced.
TL;DR: In this paper, the various types of hydrogen ion concentration gradients formed along a chromatographic layer during elution with mineral acids, buffer solutions, and neutral salt solutions were thoroughly investigated.
01 Jan 1969
TL;DR: Asplenium petrarchae (Guerin) DC.
Abstract: SUMMARY Asplenium petrarchae (Guerin) DC. has been found for the first time in Sardinia (Capo Figari, NE part of the island). On the basis of herbarium material and of literature, the distribution area of the species, which is much fragmentary, is illustrated.
TL;DR: In this article, the mean square displacements in three directions for the atoms of the Ni(110) surface are calculated by means of a simplified treatment, using a Morse potential function.
TL;DR: In this article, the E.P.R. relaxation of the SO2-Radial-ion in water solution has been studied as a function of temperature and viscosity, and the analysis of all possible broadening mechanisms shows that the spin-rotational interaction is the only process effective on linewidth.
Abstract: The E.P.R. linewidth of the SO2 - radical-ion in water solution has been studied as a function of temperature and viscosity. A strict dependence of the linewidth on T/η has been observed over the range of temperature and viscosity examined. The analysis of all possible broadening mechanisms shows that the spin-rotational interaction is the only process effective on the linewidth. The theory extended by Atkins and Kivelson [3] to E.P.R. relaxation has been checked quantitatively. From the slope of ΔH versus T/η and the principal values of the g tensor of the SO2 - radical-ion, the value of the hydrodynamic radius is r = 0·91 a. Comparison with the linewidth of the ClO2 isoelectronic radical has been made.
TL;DR: Some years ago this group suggested that microvascular endothelium may be considered as one of the regulators of kinin metabolism on the basis of the following data: arterial kininogen is slightly higher than that of venous, indicating a high capillary clearance.
TL;DR: In this paper, the mean lives of the first excited states in 29P and 29Si have been measured with the Doppler shift attenuation methods as τm = 0.18±0.03 and 0.43± 0.05 ps, respectively.
TL;DR: In this article, the problem of finding trajectories of a linear evolution equation connecting two prescribed sets of states, initial and terminal, in the shortest possible time is formulated in the form of a maximum principle.
Abstract: The problem is that of finding trajectories of a linear evolution equation connecting two prescribed sets of states, initial and terminal, in the shortest possible time. Necessary conditions for the existence of solutions, i.e., time-optimum trajectories, are given in the form of a maximum principle.
TL;DR: In this paper, the authors derived the occultation curves of three sources of the S-component present on the disk and compared the obtained electron density distributions with various models of active regions.
Abstract: The eclipse of May 20, 1966 was observed at the wavelengths of 3.2 and 9.1 cm by three Arcetri expeditions. The curves obtained by deriving the occultation curves have been filtered by digital techniques to cut off high frequency noise; by them, many characteristics of three sources of the S-component present on the disk have been studied: temperature, dimensions, emitted flux and brightness distribution. Isophotes of the latter are compared with isophotes of the corresponding Hα plages for two sources: a close similarity results for one of them. Moreover it is shown that: (a) the height above the photosphere of the sources at λ = 9.1 cm is greater than that of the sources at λ = 3.2 cm; (b) the maximum of the radio emission is not always placed exactly above a sunspot or above the sunspot group barycentre. Fitting the observed brightness temperatures, as frequency functions, by a power law and using a temperature model of an active region, the electron density distribution can be deduced. The obtained electron density distributions are compared with various models of active regions.
TL;DR: In this paper, 5-Isoxazolylhydrazines III were obtained from 5-isoxazolones I via 5-haloisoxoxazoles II.
TL;DR: In this article, the voltammetric behavior of the aqueous system I − I 2 I 2 IBr − I − + IBr and IBr + Cl − on a platinum microelectrode with periodical renewal of the diffusion layer allowed the nature of the equilibria present in the solution to be determined.
TL;DR: In this paper, the reduction of bromate in HClO4>3 M on a smooth pre-oxidized platinum microelectrode with periodical renewal of the diffusion layer was shown to occur through an autocatalytic cycle where bromine acts as electroactive intermediate.