Showing papers by "University of Cagliari published in 1970"
TL;DR: In this article, the band structure of the spinal-type semiconductor Cd${In}${S}$ has been calculated by the empirical-pseudopotential method, and the form factors have been determined with the values previously chosen by Cohen and Bergstresser for semiconductors with diamond and zinc-blende structures.
Abstract: The band structure of the spinal-type semiconductor Cd${\mathrm{In}}_{2}$${\mathrm{S}}_{4}$ has been calculated by the empirical-pseudopotential method. The form factors have been determined to agree with the values previously chosen by Cohen and Bergstresser for semiconductors with diamond and zinc-blende structures. Because of the large number of atoms per unit cell, a simplified model of the actual crystal structure has been developed, thus obtaining a feasible way to get meaningful results and to make direct comparisons with the band structures of many well-known elementary and binary semiconductors. The band structure obtained with the use of our model, and the results of the full calculations made for symmetry points, are discussed and compared with the available experimental information.
40 citations
TL;DR: In this article, the band structures of Mg2Si, mg2Ge, ng2Sn, and the solid solution Mg 2(Ge, Sn) are calculated with an a priori version of the pseudopotential method.
Abstract: The band structures of Mg2Si, Mg2Ge, Mg2Sn, and of the solid solution Mg2(Ge, Sn) are calculated with an “a priori” version of the pseudopotential method. In the computation of the Mg form factors the Heine-Abarenkov model potential and a Penn-type dielectric function have been used. Our results settle the disagreement between previous calculations and recent experimental information.
37 citations
TL;DR: In this article, the effect of γ-ray collimation geometry in measuring Mossbauer absorption spectra is studied quantitatively, and it is found that the spectra undergo an expansion around zero velocity.
20 citations
TL;DR: The results indicate that CPZ, like reserpine, causes an intraneuronal destruction of dopamine, and suggest that the well‐documented increase in dopamine synthesis after CPZ is the consequence of this mechanism and not of a blockade by CPZ of the dopaminergic receptors in brain.
Abstract: — In rabbits, the sedative effect of chlorpromazine (CPZ) is temporally correlated with a decrease in dopamine and a rise in homovanillic acid (HVA) in the basal ganglia Reserpine elicits similar biochemical changes In addition, both reserpine and CPZ reduce the concentration of 3-methoxytyramine, the O-methylated metabolite of dopamine in the basal ganglia of normal rabbits In contrast, both drugs markedly increase the levels of this metabolite in animals treated with a monpamine oxidase inhibitor The results indicate that CPZ, like reserpine, causes an intraneuronal destruction of dopamine, and suggest that the well-documented increase in dopamine synthesis after CPZ is the consequence of this mechanism and not of a blockade by CPZ of the dopaminergic receptors in brain
16 citations
01 Jan 1970
TL;DR: In this paper, a method was described for finding the actual line shape of an absorption line, or the Bloch decay, in nuclear magnetic resonance, given only a limited number of moments of the line.
Abstract: A method is described for finding the actual line shape of an absorption line, or the Bloch decay, in nuclear magnetic resonance, given only a limited number of moments of the line. The line shape found is the most probable one, given the information available. If only the second moment is known, for example, the most probable line shape is gaussian.
14 citations
TL;DR: The stimulatory effect of scopolamine was not affected in inexperienced rats but was antagonized in the experienced animals, and the effect of amphetamine on exploratory behaviour was investigated in a Y shaped runway on inexperienced and experienced male albino Wistar rats.
12 citations
TL;DR: The two alpha blockers neither affected the spontaneous ACh output nor the increase evoked by RF stimulation and by amphetamine administration, and propranolol and pronethalol did not affect the spontaneous output nor prevented the increase associated with RF stimulation.
10 citations
7 citations
TL;DR: This paper presents a meta-analyses of the diffraction and crystal structure of the Na6(CO3/ Na4(SO4)/ Na2SO2 mixture obtained during the collection and characterization of Na2CO3 at the resolution of the E-modulus of the Higgs boson.
7 citations
TL;DR: It appears that midbrain structures lying between the midpontine pretrigeminal level and the collicular level exert not only the already described effect on ACh content of the cerebral cortex but also influence GABA content, possibly through the control of an inhibitory cortical system releasing GABA at the synaptic endings.
5 citations
TL;DR: In sodium phosphate buffer pH 8.5, at 38 °, pyridoxal-5-phosphate catalyzes α-β elimination reactions on lanthionine and cystathionine, with production of ammonia, pyruvate, and cysteine, or homocysteines, respectively.
TL;DR: Males of Urosimulium stefanii Cont.
Abstract: Males of Urosimulium stefanii Cont., (1963) from various populations in Sardinia, differ from females by a long asynaptic region in one pair of salivary gland chromosomes. This asynaptic tract does not seem to be due to inversions but rather to large structural changes. In meioses of the male, a pair of chromosomes does not show interstitial chiasmata. It is suggested that this pair of chromosomes represents the sex chromosome pair. The evolutionary process has been discussed.
TL;DR: In this paper, the effects of collimation geometry on Mossbauer peaks when the absorber is thick were investigated and equilibria were derived to account for the effect of the geometry effect.
TL;DR: Guanidine inhibits both the replication of poliovirus RNA and the appearance in infected cells of an active RNA polymerase, without affecting the overall synthesis of virus-coded proteins.
TL;DR: In this article, the definition of the rheological model of concrete, or uncracked reinforced concrete, in the field of dynamic stresses sufficiently far from breaking, is attempted; an aim towards which we had already recently directed a series of investigations to clarify the different aspects of experimental behaviour.
Abstract: The definition of the rheological model of concrete, or uncracked reinforced concrete, in the field of dynamic stresses sufficiently far from breaking, is here attempted; an aim towards which we had already recently directed a series of investigations to clarify the different aspects of experimental behaviour.
TL;DR: The existence of the 2 + excited state at 30 MeV in 4 He is strongly favoured by calculations that include the interaction between the outgoing deuterons in the reaction 4 He( γ, d)d as discussed by the authors.
TL;DR: Investigation of fusidic acid, a steroidal antibiotic, shows that the antibiotic also inhibits the reactions for peptide chain initiation, possibly by interfering with the initiation factor F1, however, at low concentrations ( 5 · 10−3 M) are required to inhibit the responses for peptides chain initation.
TL;DR: In this paper, an equation is given which enables us to evaluate the statistical fluctuations when a function is determined by means of several experimental points, analogous to the well-known formula of standard deviations, and is deduced from a distribution that substantially is a generalization of the Γ distribution.
TL;DR: In this paper, a method for measuring the velocity amplitude of small oscillations by means of Mossbauer efects is described, and theoretical equations are deduced which enable conditions for the best sensitivity to be determined.
TL;DR: In this article, the role of visual dominance on the surroundings in relation to waterways and natural access routes was evaluated with the aid of GIS methodologies such as viewshed and cost surface analysis.
Abstract: One of the most important megalithic groups in Western Europe in terms of number and characteristics is the group of over 200 monuments of various types in Sardinia. It now seems to be confirmed that the rise of the megalithic phenomenon was during the culture of San Michele of Ozieri (Late Neolithic, 4000-3300 B.C.E.). The Sardinian dolmen graves, however, had a maximum distribution during the Chalcolithic, as evidenced by most of the finds from excavations. The phenomenon also shows a close relationship beyond Sardinia and especially with the monuments of Catalonia, Pyrenees, non-coastal departments of French-midi, Corsica and Puglia.
About 90 dolmen graves of various types have been investigated, namely the simple type, “corridor” type, “allee couverte” type, and others of uncertain attribution, located in central-western Sardinia, and particularly in a significant area of ca. 3500 km2 coinciding with the historical regions of Marghine-Planargia, Middle Valley of Tirso and Montiferru. This includes some 40% of all Sardinian dolmens. Locational trends and relationships with regard to landscape elements were studied with the aid of GIS methodologies such as viewshed and cost surface analysis. This allowed an evaluation of the role of visual dominance on the surroundings in relation to waterways and natural access routes.
These dolmens enjoy an isolated positional character, being found more often in high plateaus, but also on low plateaus and hills. Although different concentrations are found in dolmenic graves, these do not seem to have any direct relationship among them, but their influence is apparently directed towards travel routes and sensitive elements of the landscape that have capabilities of territorial demarcation.
The particular location emphasizes the significance of these monuments as territorial markers for segmentary societies. It seems that a dolmen was constructed according to the territory immediately surrounding it. This reinforces the hypothesis of there being a secondary task, in addition to that of burial, to symbolize a message or landmark for those who moved towards "another" territory: a sign of belonging.
TL;DR: It is concluded that derivatives of aminohexoses substituted at C-1 with a dioxopentyl chain are the precursors of 2-methylpyrrole in the Cessi & Serafini-Cessi (1963) modification of the Elson-Morgan reaction.
Abstract: 1-C-(1-Acetylacetonyl)-2-deoxy-2-(1-methyl-3-oxobut-1-enyl)amino -d-galactitol is obtained from the condensation of 2-amino-2-deoxy-d-galactose with pentane-2,4-dione in anhydrous solvent. On treatment with hot alkali it gives 2-methylpyrrole with 37% yield. By acid hydrolysis under mild conditions the compound loses the N substituent and from the resulting unstable derivative 2-methylpyrrole is obtained (52% yield). It is concluded that derivatives of aminohexoses substituted at C-1 with a dioxopentyl chain are the precursors of 2-methylpyrrole in the Cessi & Serafini-Cessi (1963) modification of the Elson–Morgan reaction. As demonstrated previously, products of condensation of aminohexoses with pentane-2,4-dione at the amino group are not converted directly into 2-methylpyrrole, but this step provides protection of the amino group during condensation at C-1.
TL;DR: In this paper, it was shown that the unitarization of the Born approximation with the use of the Van Oers-Seagrave formula for the radiative capture of thermal neutrons by deuterons to form tritium yields correction to the Born approximations of the same order of magnitude obtained with the classical effective range formula.
01 Jan 1970
TL;DR: In this paper, the authors compare the politikon dikaion with the politeia reale, a specie of giustizia defined by Aristotele in the quinto libro dell’ Etica Nicomachea, in order to rendere intelligibili i fattori politi (indipendenti cioe dalla natura, dalla necessita or dal caso).
Abstract: Nel quinto libro dell’ Etica Nicomachea Aristotele definisce la condizione necessaria perche una particolare specie di giustizia, il giusto politico ( politikon dikaion ), trovi attuazione: e l’esistenza di un ordine politico formalmente definito ( politeia ). Al centro della riflessione aristotelica sul giusto politico e il rapporto che passa tra questa particolare modalita di configurazione della giustizia e la politeia reale. E infatti la comprensione di quel rapporto a rendere intelligibili i fattori politici “indipendenti” (indipendenti cioe dalla natura, dalla necessita o dal caso) che condizionano la storia delle comunita politiche e che costituiscono l’oggetto di studio proprio della scienza politica. Attraverso la comparazione con la politeia Aristotele riflette sull’intelligibilita del giusto politico: in quanto si discosta dalla nozione assoluta di giustizia, come la politeia reale si discosta da quella ideale, il giusto politico diventa intelligibile.
TL;DR: The activity of ribosomes washed with high concentrations of ammonium chloride may be restored by adding initiation factors prepared from E. coli to carry out the ApUpG-dependent reactions for peptide chain initiation demonstrated for Escherichia coli ribosome.
Abstract: Ribosomes prepared from the bacterium Bacillus subtilis, from mitochondria of Neurospora crassa and from chloroplasts of Euglena gracilis carry out the ApUpG-dependent reactions for peptide chain initiation demonstrated for Escherichia coli ribosomes. Initiation factors functionally similar to those from E. coli appear to be present on the above reported ribosomal preparations. The activity of ribosomes washed with high concentrations of ammonium chloride may be restored by adding initiation factors prepared from E. coli.
01 Oct 1970
TL;DR: In this article, a phase sensitive detector using a mercury relay is described, whose application are complementary to those of conventional circuits, even though being unable to behave correctly beyond some tens of Hz.
Abstract: 2014 A phase-sensitive detector using a mercury relay is described, whose application are complementary to those of conventional circuits. It can work precisely at frequencies as low as 0.1 Hz, even though being unable to behave correctly beyond some tens of Hz. REVUE DE PHYSIQUE APPLIQUÉE TOME 5, OCTOBRE 1970, PAGE On sait que les détecteurs synchrones communs travaillent correctement dans un intervalle de fréquence qui, en partant de quelques Hz, ne descend jamais au-dessus de 1 Hz environ [1, 2, 3]. Néanmoins, dans certaines applications, il faudrait, à cause de la nature particulière du problème en question, employer des fréquences encore plus basses, par exemple 0,1 Hz ou encore moins. Clairement, la difficulté la plus considérable pour atteindre des fréquences aussi basses, dérive de la stabilité limitée du circuit électronique du détecteur [4]. Dans le but d’éviter cet obstacle nous avons projeté un détecteur synchrone, en utilisant un relais. En réalité, dans les travaux des pionniers sur le rejet du bruit on avait déjà usé des interrupteurs mécaniques [5, 6]. Cependant ces dispositifs par la suite n’ont pas été développés de façon à jouir des excellentes prestations des relais modernes. Dans la figure 1 on montre le circuit que nous avons utilisé. Le signal sinusoïdal de référence, traversant un circuit de déphasage approprié et un amplificateur saturé, alimente le bobinage du relais. Le montage est du type double (’) et fonctionne par des contacts à mercure qui permettent une fréquence maximale de 300 Hz. Le signal d’entrée est appliqué directement au circuit intégrateur RC et on le renverse périodiquement selon la phase de la référence. L’amplificateur du canal de référence actionne le relais lorsque le signal de référence atteint 10 mV. Si la valeur de crête du signal de référence est de 1 V, ceci correspond à un déphasage de moins de 10. Le déphaseur RC a été projeté surtout pour corriger le retard sur la commande du relais. Pour cette raison il agit (1) SEEN BNHWY 2 RT. seulement pour avancer la phase de la référence. Pour des fréquences de quelques dizaines d’Hz on peut utiliser les valeurs Cl = 1 03BCF et R1 = 0,5 M03A9 Lorsqu’il faut atteindre des fréquences de près de 0,1 Hz, on demande des valeurs de Cl plus élevées, jusqu’à 100 03BCF. Mais, au niveau de ces fréquences et au-dessous, on peut éliminer Cl parce qu’il devient inutile de compenser le retard du relais, qui est bien petit en comparaison de la période du signal de référence ( 10 s). Comme premier stade de l’amplicateur d. c. on a utilisé un transistor a effect de champ dans le but d’obtenir l’impédance d’entrée élevée demandée pour le bon fonctionnement du déphaseur. La résistance du drainage doit être choisie de façon que le voltage sur l’émetteur du transistor BSX 12 soit légèrement plus petit que la tension de rupture de la diode Zener. De cette façon on atteint à la sensibilité de commande maximale. Il faut que la constante de temps de l’intégrateur soit au moins une dizaine de fois plus grande que la période du signal dans le but d’éviter les fluctuations du signal de sortie. Pour cette raison, on demande des valeurs de pour travailler à 0,1 Hz. Dans la figure 2 on montre le bon fonctionnement du détecteur à la fréquence de 30 Hz. Le point de potentiel zéro qui apparaît dans la photo exécutée avec le signal de référence hors de phase, correspond au temps de commutation du relais. A des fréquences plus élevées ( N 50 : 200 Hz), au contraire, le comportement est moins satisfaisant, et ce à cause d’une certaine indécision dans l’obtention du contact. Dans nos expériences, le voltage sur la capacité d’intégration a été mesuré par un voltmètre élecArticle published online by EDP Sciences and available at http://dx.doi.org/10.1051/rphysap:0197000505077700