Showing papers by "University of Florence published in 1983"
TL;DR: In this article, the structure of the jet final state and its phenomenological consequences are discussed, and a review of QCD results for these quantities and corresponding infrared resummation techniques are presented.
458 citations
TL;DR: The effect of GM1 ganglioside on the recovery of nigro-strital dopaminergic neurons was studied in rats after unilateral hemitransection and it is found that repeated administration ofGM1 significantly increased the HVA content, the tyrosine hydroxylase activity and the tyosine hydoxylase-related immunofluorescence in the striatum ipsilateral to the lesion.
250 citations
TL;DR: In this paper, the effect of primordially produced gravitons on the anisotropy of the cosmological microwave background radiation was investigated and an upper limit on the associated vacuum energy density was derived.
238 citations
TL;DR: The history of land mammals is characterized by dispersal events, i.e. short periods of rapid intercontinental migrations and faunal replacements as mentioned in this paper, which are characterized by a practically total rejuvenation of the fauna with the appearance of new types of adaptation.
184 citations
TL;DR: Results indicate that ammonium ions increase the release and the formation of glutamic acid in the brain and may be one of the mechanisms of ammonia toxicity in vivo.
Abstract: The effects of ammonium ions on the release of glutamic acid from the rat cerebral cortex were measured in vivo using cortical cups and a multiple ion detection technique. The neosynthesis of this amino acid from glucose was also studied in two experimental models of hepatic encephalopathy: (1) rats receiving large amounts of ammonium acetate (i.p.) and (2) rats with a surgically constructed portocaval anastomosis. Intraperitoneal administration of 8 mmol/kg of ammonium acetate increased the cortical release of glutamic acid from 9.1 +/- 0.8 to 19 +/- 2 (nmol X cm-2 X min-1). Moreover, 20 min after ammonium acetate administration the rate of incorporation of 13C2, originating from [13C]glucose, into glutamic acid increased by 65%. In several brain areas of rats bearing a portocaval anastomosis and fed ad libitum for 4 weeks, the content of glutamic acid slightly increased and the rate of formation of [13C2]glutamate from [13C]glucose approximately doubled. These results indicate that ammonium ions increase the release and the formation of glutamic acid in the brain. The resulting increased concentration of this amino acid in the extracellular spaces may be one of the mechanisms of ammonia toxicity in vivo.
137 citations
TL;DR: In the newborn and 7 day-old pups acetylcholine release was approximately 50% lower than that of the 3 month-old rats at all frequencies tested, and beginning with this age the evoked ACh release underwent a decline which in the 24 month- old rats brought it back to the same level as in the newborn ones.
117 citations
100 citations
79 citations
TL;DR: It is concluded that morphine and somatostatin are as effective as ergotamine in reducing the pain of CH and all three drugs are significantly more active than placebo.
Abstract: Substance P appears to be involved in the transmission of pain signals from the periphery to the spinal cord and brain stem. Substance P containing neurons are responsible for the neurogenic vasodilation identical to that obtained by substance P release evoked by antidromic stimulation of these fibres. Both endogenous opioids and somatostatin inhibit the release of substance P from central and peripheral endings. Present pharmacological investigations conclude that morphine and somatostatin are as effective as ergotamine in reducing the pain of CH. All three drugs are significantly more active than placebo. Somatostatin and opiates could act by inhibiting the release of substance P.
73 citations
TL;DR: In this paper, the behavior of the [Ru2(CO)4(CH3COO)2]n/tributylphosphine/acetic acid system has been investigated as a function of reaction conditions and molar ratios of reactants.
69 citations
TL;DR: The investigation of the conversion of 1-14C arachidonic acid by vascular tissue indicated that human vascular tissues produce the metabolites of the cyclooxygenase dependent pathway and that prostacyclin is the main metabolite with a PGI2/TxA2 ratio of 4:1.
TL;DR: In this paper, the Fermi-Pasta-Ulam model has been studied following the time evolution of the space Fourier spectrum through the numerical integration of the equations of motion for a system of 128 non-linearly coupled oscillators.
Abstract: The Fermi-Pasta-Ulam model has been studied following the time evolution of the space Fourier spectrum through the numerical integration of the equations of motion for a system of 128 non-linearly coupled oscillators. One-mode and multimode excitations have been considered as initial conditions; in the former case, an approximate analytic technique has been applied to describe the "short-time" behavior of the system, which fits well the experiment. The main result in both cases is the presence of different stationary states towards which the system is evolving: a $\frac{1}{{k}^{2}}$ spectrum (corresponding to the equipartition of energy) or an exponential spectrum can be reached, depending on the value of some parameter, which takes into account the relative weight of the nonlinear to the linear term of the equations of motion.
TL;DR: The results support the hypothesis that Asp and Glu are excitatory neurotransmitters in intrinsic hippocampal circuits and are possibly released from the Schaffer collaterals and commissural fibres.
Abstract: The release of endogenous aspartic, glutamic, and gamma-aminobutyric acids (Asp, Glu, GABA, respectively) was measured in the effluent from superfused hippocampal slices using a new and sensitive mass spectrometric method. The stimulation of the stratum radiatum of the rat dorsal hippocampus caused a Ca2+-dependent increase in the release of these amino acids. This release was accompanied by an increase in the incorporation of [13C2] from [13C]glucose into Asp, Glu, and GABA, suggesting an increase in their neosynthesis. The removal of Ca2+ from the superfusion fluid brought about a marked decrease in Asp and Glu release at rest, and prevented their stimulation-evoked release and the appearance of population spikes. The results support the hypothesis that Asp and Glu are excitatory neurotransmitters in intrinsic hippocampal circuits and are possibly released from the Schaffer collaterals and commissural fibres. The increase in GABA release and neosynthesis during stimulation of the stratum radiatum could be related to recurrent inhibition evoked by transsynaptic stimulation of the pyramidal cells.
TL;DR: The sequence of polarity zones established by Alvarez and others for the Cretaceous and Paleocene in the Scaglia Formation in the Bottaccione Gorge at Gubbio has now been extended through the uppermost Paleocene into the upper Eocene Globigerinatheka semi-involuta zone.
Abstract: The sequence of polarity zones established by Alvarez and others for the Cretaceous and Paleocene in the Scaglia Formation in the Bottaccione Gorge at Gubbio has now been extended through the uppermost Paleocene into the upper Eocene Globigerinatheka semiinvoluta zone (= anomaly 18). The relationships between the standard Paleogene foraminiferal zones and the sea-floor anomalies are defined, with the exception of the mid-Eocene zones of Morozovella lehneri , Orbulinoides beckmanni , and the base of the Truncorota-loides rohri zone, which are obscured by inadequate preservation and a fault gap. The base of the Eocene lies above anomaly 25; the lower to middle Eocene contact (base Lutetian) lies in the upper part of anomaly 22; the base of the Bartonian lies below the base of anomaly 18; and the base of the Priabonian (upper Eocene) lies within anomaly 18. Radiometric ages appear to diverge systematically from a geochronology based on steady sea-floor-spreading rates, suggesting that spreading may have been as much as a factor of 3 slower in the Paleocene and the late Eocene than in the early and middle Eocene.
TL;DR: Adenosine, in concentrations ranging from 1 to 100 microM, reduced in a dose-dependent manner the release of acetylcholine and was more active on the stimulated than on the resting release, however, the fractional reduction by adenosine of stimulated release of ACh did not vary with increasing stimulation rate.
TL;DR: In this article, a triphos ligand was used to synthesize a compound that was shown to have a crystal structure similar to that of the previously obtained platinum isomorph.
TL;DR: In this article, the reactions of 2-amino-2(hydroxymethyl)-1,3-propanediol (TRIS, THAM) with H+, Ni2+, Cu2+, and Zn2+ ions have been studied at 298 K in aqueous solutions (0.15 mol dm−3 NaCl).
TL;DR: Data strongly point to a pivotal role of complement system in the pathogenesis of hemodialysis leukopenia as well as the in vivo effects of four different dialyzer membranes on leukocytes and complement levels in vitro.
TL;DR: It is concluded that homotaurine is a competitive antagonist of GABAB mediated effects in the guinea‐pig ileum, thus showing no GABAA receptor‐mediated interference.
Abstract: Homotaurine (3-aminopropane sulphonic acid) did not inhibit the twitch response in guinea-pig ileum longitudinal muscle whilst gamma-aminobutyric acid (GABA) and (-)-baclofen evoked dose-dependent inhibitions. The inhibitory effects of GABA and (-)-baclofen were prevented in the presence of homotaurine 2 X 10(-4) and 10(-3) M. The log dose-effect curves of GABA and (-)-baclofen were shifted in a parallel manner compatible with competitive antagonism. The pA2 of homotaurine with GABA (4.22 +/- 0.05) and (-)-baclofen (4.26 +/- 0.1) were the same. Homotaurine did not antagonize the inhibitory effects of morphine (ED50 4 X 10(-7) M), noradrenaline (ED50 10(-6) M) or ATP (ED50 1.5 X 10(-5) M). The inferior homologue of homotaurine, taurine 10(-3) M, did not modify the inhibitory effects of GABA and (-)-baclofen. Picrotoxin 5 X 10(-5) M antagonized GABAA receptor-mediated contraction but did not affect GABAB receptor-mediated inhibition. At the same concentration the drug did not influence the antagonistic action of homotaurine, thus showing no GABAA receptor-mediated interference. It may be concluded that homotaurine is a competitive antagonist of GABAB mediated effects in the guinea-pig ileum.
TL;DR: A patient with an abnormally expanded population of circulating lymphoid cells displaying the features of the so-called large granular lymphocytes (LGL) displayed natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) activities comparable to those of normal peripheral blood mononuclear cells, or even higher, and did not respond to T-cell mitogens or allogeneic cells.
Abstract: This paper reports the case of a patient with an abnormally expanded population of circulating lymphoid cells displaying the features of the so-called large granular lymphocytes (LGL). These cells were peroxidase negative and nonphagocytic, formed rosettes with sheep erythrocytes, had receptors for IgG, and contained azurophilic (electron-dense) granules. Like normal LGL, the patient cells were positive for two acid hydrolases (acid phosphatase and β-glucuronidase) but did not stain for α-naphthyl acetate esterase (ANAE), which is present in normal LGL. Ultrastructural studies revealed that the patient cells were rich in Golgi-derived vesicles, coated vesicles, multivesicular bodies, and immature granules, indicating that, unlike normal LGL, they were engaged in granulogenesis. These features, together with the absence of ANAE activity, are suggestive of some degree of cell immaturity. The patient cells displayed natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) activities comparable to those of normal peripheral blood mononuclear cells, or even higher, and did not respond to T-cell mitogens or allogeneic cells. Furthermore, they were incapable of suppressing normal T-cell proliferation or pokeweed mitogen-induced B-cell differentiation. Analysis of the NK activity at the single-cell level revealed that a large proportion of the patient cells bound to the K562 target cells but could not accomplish the entire lytic process. This finding supports further the possibility that the patient cells were immature LGL. The surface phenotype of the patient cells (as defined by a battery of monoclonal antibodies) was somewhat different from that usually observed in the majority of the normal LGL because, in addition to the HNK-1 marker, the cells were OKT3+, aLeul+, aLeu4+, OKT8+, aLeu2a+, and 3A1+ but were OKM1− and 4F2−. This phenotype could correspond to that of maturing LGL.
TL;DR: The chemisorption of iodine vapor on the three low index faces of silver single crystals has been studied by combined LEED, AES and thermal desorption mass spectrometry.
TL;DR: In this article, the effects of soil temperature and soil moisture content on the rate of simazine degradation were measured in the laboratory in soils from sixteen sites located in several different countries.
Abstract: Summary
The effects of soil temperature and soil moisture content on the rate of simazine degradation were measured in the laboratory in soils from sixteen sites located in several different countries. First-order half-lives under standard incubation conditions were significantly correlated with clay content, organic carbon content and soil pH in a multiple linear regression. The temperature dependence of degradation was similar in the different soils whereas the moisture dependence showed considerable variation between soils. Persistence of simazine was also measured in the same soils in the field and at live additional sites. Weather records from the different sites for the periods of the Held experiments were used in conjunction with constants derived from the laboratory data in a computer program to simulate persistence in the field. In general, the model overestimated residues in the field. About half of the calculated residues were within 25% of those observed, an accuracy sufficient for practical purposes, but on several occasions the discrepancies between calculated and observed residues were greater than 50%. Possible reasons for the discrepancies and requirements for further experiments are discussed.
Resume
EWRS groupe de travail herbicide-sot: experience en collaboration sur la persistante de la simazine au sol
L'influence de la temperature du sol ainsi que du contenu en humidite sur la rapidite de degradation de la simazinc a ete mesuree au laboratoire dans des sols provenant de seize emplacements situes dans plusieurs pays. Dans des conditions normales d'incubation, des demi-vies de premier ordre se trouvaient en correlation significative avec le contenu en argile et en carbone organique ainsi qu'avec le pH du sol. par regression lineaire multiple, Le rapport entre la temperature et la degradation etait pareil dans les dilVerents sols tandis que Ie rapport a Thumidile variait de fai;on considerable. La persistance de la simazine a ele mesuree aussi en plein champ et a cinq emplacements supplementaires, Des donnees meteorolo-giques concernant les difl'erents emplacements pendant la duree des experiences onl servi. en combinaison avec des constantes provenanl de donnees obtenues en laboratoire. a former un programme machine qui simule la persistance en plein champ. En general le modele a surestitne les residus au ehamp, A peu pres la moilie des residus calcules s'accordaienl a une ±25 npres aux observations de plein champ, ce qui represente une precision suffisante dans la pratique. Plu-sieurs fois, cependant. les desaccords entre les calculations et les residus observes depassaient 50% La discussion porte sur Porigine de ces desaccords ainsi que sur les moyens exiges pour des experiences ulterieures.
Zusammenfassung
EWRS Hertiizid-Boden Arheitsgruppe: Zu.sam-menarfwit twi cinvm Versuch zur Pcrsistenz von Simazin im Boden
Der Einfluss der Bodentemperalure sowie des Bodenfeuclitigkeitgehaltes auf die Abbaurate von Simazin wurde in Laborversuehen bei Boden aus sechszehn in verschiedenen lander gelegenen Grundstiicken gemessen, Unier normalen Inku-bationsbedingungcn standen Halbwertszeiten er.ster Ordnung in bedeutungsvoller Wcchselbc-ziehung mit dem Gehalt an Lehm und organis-chem KohlstofT und mil dem pH des Bodens in einer vielfachen lineareii Regression, Die Tem-peraturabhangigkeit des Abbaus war gleich in den verschiedenen Boden. wahrend die Feuchtig-keitsabhiingigkeit merkbare Unierschiede zrwisehen den Boden zeigte. Die Persistenz von Simazin wurde auch in Freilandsversuchen in denselben Boden und an fiinf zusatzlichcn Grundstucken gemessen. Wetterberichte von den versehiedenen Grundstucken warhrend des Zeit-verlaufs der Freilandversuehe wurden in Zusam-menhang mit von Laborangaben derivierten Konstanten in einem Compuierprogramm ver-wendet. um die Persistenz im Feld zu simulieren, I m Allgemein iiberschiitzte der Modell die Riick-stande im Feld. UngeHihr die Halfte der ausger-echnetcn Riiekstande standen innerhalb ±25% derjenigen. die im Feld bemerkt waren. was. praktisch gesehen. eine ausreichende Genauigkeit bietet, Mehrere Male aber waren die Unters-chiede zwischen ausgcrechnetc und benierkte Ruckstande mehr als 50%. Mogliche Ursachen dieser Unterschiede sowie Forderungen fur wei-tere Versuche werden diskutiert.
TL;DR: A greater decrease in the serum concentration of bilirubin was found in subjects exposed to the green light when compared with infants exposed to daylight lamps, so the use of green light is strongly suggested instead of the white, blue, and special blue lamps, because of the real efficiency, power and range of wave lengths.
Abstract: Photodegradation of bilirubin in vivo has been investigated by using green fluorescent sources according to the suggestions obtained in a previous study in vitro. Two groups of 50 jaundiced low-birth-weight infants were exposed to fluorescent light in phototherapy units under similar irradiant conditions. One group was exposed for 24 h to standard green tubes, the other, to daylight lamps. Newborns of the two groups were similar for gestational age, birthweight, and initial bilirubin concentration. A greater decrease in the serum concentration of bilirubin was found in subjects exposed to the green light when compared with infants exposed to daylight lamps. The use of green light is strongly suggested instead of the white, blue, and special blue lamps, because of the real efficiency, power and range of wave lengths.
TL;DR: In this article, the ESR of the neutral spin probe 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl in the study of its dynamics of water adsorbed onto silica gels with pore diameters in the range 4 to 100 nm is described.
TL;DR: The structure of the compound [(np 3 )Ni(P 4 Se 3 )]·2C 6 H 6, obtained from reaction of the nickel(0) complex with tris(2-diphenylphosphinoethyl)amine, has been determined by X-ray diffraction studies as discussed by the authors.
TL;DR: The two-photon excitation spectrum of pyrene and the polarization ratio Ω have been measured up to ≈2100 A. as discussed by the authors showed evidence of a strong vibronic coupler.
TL;DR: In this article, the authors compare the two methods of deriving interaction-induced pair polarizabilities from collision-induced, depolarized spectra, namely classical line shape and moment analysis.
Abstract: We compare the two methods of deriving interaction-induced pair polarizabilities from collision-induced, depolarized spectra, namely classical line shape and moment analysis. We discuss their limitations and show that the joint use of line shape and moment analysis leads to the determination of an empirical pair polarizability anisotropy model which has maximal consistency with the available experimental results. We have applied the combined method to the pair spectrum of argon at room temperature (298 K) as an example.
TL;DR: In this paper, a high-frequency solution for the scattering of a plane wave at the edges of surface impedance discontinuities on a fiat ground plane is presented for both the transverse electric (TE) and transverse magnetic (TM) cases.
Abstract: A high-frequency solution is presented for the scattering of a plane wave at the edges of surface impedance discontinuities on a fiat ground plane. Arbitrary uniform isotropic boundary conditions and a direction of incidence perpendicular to the edges of the discontinuities are considered for both the transverse electric (TE) and transverse magnetic (TM) cases. An asymptotic approximation of the exact solution given by Maliuzhinets and a spectral extension of the geometrical theory of diffraction (GTD) are used. Uniform expressions for the scattered field received at a point on the surface are given, including surface wave contributions. Numerical results are shown and in some examples they are compared with those obtained from a moment method (MM) solution.
TL;DR: In this article, the nature of the eo-Alpine high-pressure recrystallization, and the origin of the protoliths are the subjects of the article, where they show the effects of a pervasive, essentially isochemical, high pressure Early Alpine metamorphism for which a sequence of mineral assemblages is partially preserved.
Abstract: Aluminous, magnesian metagabbroic layers and pods occur in the Beigua serpentinite of Western Liguria, where they are associated with more voluminous (Fe+Ti)-rich lithologies. Both types were subjected to localized early rodingitization. All rocks show the effects of a pervasive, essentially isochemical, high-pressure Early Alpine metamorphism for which a sequence of mineral assemblages is partially preserved: eclogite → glaucophanic eclogite → Na+Al actinolitic amphibolite → greenschist. The nature of the eo-Alpine high-pressure recrystallization, and the origin of the protoliths are the subjects of this paper.