Showing papers by "University of Florence published in 1986"

Polarization diversity in radars

Abstract: Polarization, together with the amplitude, time, frequency, phase, and bearing descriptors of radar signals, completes the information which can be obtained on target returns in monostatic radars. The exploitation of information on the echo polarization state through polarimetric radars is currently a subject of interest, due to theoretical and technological advances, as well as to the development of new radar applications. Many polarization techniques, which have been proposed and analyzed to enhance radar performance, are reviewed in this paper in order to assess the possible improvement they can provide in the signal-to-disturbance ratio, target detectability, target discrimination and resolution, and target classification and identification. Some recent experimentally based results relating to these applications are also presented. Those techniques are emphasized for which polarization-based capabilities appear sufficiently assessed, such as adaptive polarization cancellation of clutter, chaff, and jamming. Polarization Doppler processing of dual-polarization radar signals, meteorologic applications, and polarization adaptation for target detection in the clear (in free space) are also examined.

Natural history of untreated idiopathic scoliosis after skeletal maturity.

Abstract: A total of 187 random cases of untreated idiopathic scoliosis, seen from a minimum of 15 to a maximum of 47 years after the end of growth, were reviewed. All curves increased after skeletal maturity (average progression: 0.4 degrees per year). Thoracic curves tend to progress more than lumbar, lumbar more than thoracolumbar, and thoracolumbar more than double major curves. Pain was present in 114 cases (61%) and appeared more frequently in women, after pregnancies, and with fatigue. Cardiopulmonary symptoms were present in 42 patients (22%), especially those with thoracic and thoracolumbar curves greater than 40 degrees. Psychologic disturbances were found in 35 cases (19%), mostly female patients with thoracic curves greater than 40 degrees. The cosmetic appearance of these patients at long-term follow-up was better compared with that at the end of growth, even though the curves progressed. Patients with decompensation of the trunk at the end of growth seemed to improve with time. In an unselected group of patients with severe curves a mortality rate of 17% was found, twice as much as in the Italian general population.

Partial regularity of minimizers of quasiconvex integrals

Abstract: We consider variational integrals ∫ Ω F ( x , u , D u ) d x with integrands F(x, u, p) growing polynomially and of class C2 in p and Holder-continuous in (x, u). Under the main assumption that F(x, u, p) is strictly quasiconvex we prove that each minimizer is of Class C1,μ in an open set Ω0 ⊂ Ω with meas (Ω − Ω0) = 0.

Calcium channel inhibitors suppress the morphine-withdrawal syndrome in rats.

Abstract: The effects of the Ca2+-channel blockers verapamil and nimodipine, on the behavioural signs of naloxone (1 mg kg-1)-induced abstinence syndrome in morphine-dependent rats, were evaluated. The content of noradrenaline (NA) and of its metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) was measured, using high performance liquid chromatography and electrochemical detection or gas chromatography-mass spectrometry, in various brain regions of these animals. Possible interactions of nimodipine and verapamil with opioid receptors were evaluated by examining their ability to displace [3H]-naloxone binding to brain membranes. Verapamil (5, 10 and 50 mg kg-1) and nimodipine (1, 5 and 10 mg kg-1) dose-dependently reduced most of the signs of morphine abstinence. Naloxone-precipitated abstinence decreased the NA content in the cortex, hippocampus, brainstem and cerebellum. In the same brain regions the content of MHPG increased, suggesting an increased release of the amine during morphine abstinence. Nimodipine (10 mg kg-1 i.v.) did not change the content of NA or MHPG in the cortex, hippocampus and brainstem. However, nimodipine pre-treatment markedly reduced the changes in NA and MHPG content induced by the abstinence syndrome. Neither verapamil nor nimodipine displaced [3H]-naloxone from its binding sites. These results suggest that Ca2+-channel blockers suppress the behavioural and neurochemical expressions of morphine abstinence by a mechanism that differs from those of opioids or alpha 2-adrenoceptor agonists.

An early Miocene arc-tholeiitic magmatic dike event from the Alboran Sea — Evidence for precollisional subduction and back-arc crustal extension in the westernmost Mediterranean

Abstract: A discussion is made on the general significance of an Early Miocene (22–23 Ma, K/Ar dating) basaltic dike swarm that outcrops within large areas of the central and western Betic Zone of the Betic Cordilleras (Southern Spain). This dike swarm is thought to represent the remains of one of the earliest magmatic episodes within the the Neogene volcanic province that is associated with the late orogenic evolution of the Alboran region, and undoubtedly offers the best preserved igneous material related to this early stage that is known at present. The dike rocks (hypabyssal equivalents of andesitic basalts and basaltic andesites) have both major and trace-element abundance patterns that are akin to those of arc-tholeiitic suites. The field relationships and areal distribution of the dike swarm suggest, on the other hand, that a major E-W-trending rifting belt could have been developing within the Alboran Block in oligo-miocene times, previous to its collision with adjacent continental borderlands in the Early-Middle Miocene.

Zonal recovery mechanisms in talitrid crustaceans

Abstract: Zonal orientation in the seashore ecotones particularly that of littoral talitrids depends on several mechanisms, but primarily on the sun compass which compensates for the sun's apparent motion (chronometric solar photomenotaxis). The details of this mechanism have been studied in Mediterranean and North European talitrids, but above all in populations where the astronomic conditions (different apparent motion of the sun in different periods of the year) complicate this dependance on the sun compass. Another aspect of the mechanism is its innate component: laboratory‐born young of both Mediterranean and intertropical populations, when exposed to the sun for the first time, show a statistically significant directional tendency which is ecologically correct and in compliance with the original population. Crosses indicate the presence of a genetic control of behaviour with a continuous circular variability, and of a genetic difference in the escape direction of animal populations capable of chronom...

Increase in the Content of Quinolinic Acid in Cerebrospinal Fluid and Frontal Cortex of Patients with Hepatic Failure

Abstract: Quinolinic acid (QUIN), an excitotoxic tryptophan metabolite, has been identified and measured in human cerebrospinal fluid (CSF) using a mass-fragmentographic method. Furthermore, its content has been evaluated in frontal cortex obtained at autopsy from the cadavers of patients who died after hepatic coma. During the coma, the concentration of QUIN in the CSF was 152 +/- 38 pmol ml-1. In contrast, the concentration in control patients affected by different pathologies was 22 +/- 7 pmol ml-1. In the frontal cortex of patients who died after episodes of hepatic encephalopathy, the content of QUIN was three times higher than in controls (2.6 +/- 0.6 versus 0.80 +/- 0.08 nmol/g wet weight). As a result of these investigations we are now able to extend our previous observations on the increase of QUIN in the brains of rats used as experimental models of hepatic encephalopathy to man. QUIN should therefore be added to the list of compounds possibly involved in the pathogenesis and symptomatology of brain disorders associated with liver failure.

Quantum corrections to the thermodynamics of nonlinear systems.

Abstract: The path-integral approach is used for determining quantum corrections to the free energy of nonlinear systems. An effective potential, to be inserted in the configurational integral, is constructed by a new variational scheme which gives the quantum modification of the potential due to the anharmonic part together with the frequency renormalization. The single anharmonic oscillator is studied first. Then the extension to fields is presented and a new general expression for the partition function is given. The method is applied to the sine-Gordon chain and explicit calculations of the specific heat are shown.

Content of Quinolinic Acid and of Other Tryptophan Metabolites Increases in Brain Regions of Rats Used as Experimental Models of Hepatic Encephalopathy

Abstract: The content of the tryptophan metabolites quinolinic acid (QUIN), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) was measured in various brain areas of rats bearing a portocaval anastomosis (PCA) for 4 weeks, using mass fragmentography or HPLC. In these animals, the content of the excitotoxic compound QUIN increased by 75% in the cortex and 125% in the cerebellum. The content of 5-HT increased by 27% in the brainstem. No changes occurred in other brain areas. On the other hand, the content of 5-HIAA increased by 66% in the cortex, 65% in the caudate, 64% in the hippocampus, 120% in the diencephalon, and 185% in the brainstem. Probenecid administration caused a larger increase of 5-HIAA accumulation in various brain areas of PCA-bearing rats than in those of sham-operated controls. The cortical content of QUIN and 5-HIAA increased after administration of ammonium acetate (7 mmol/kg), whereas an equimolar amount of sodium acetate was inactive. These results confirm that profound changes in the disposition of tryptophan occur in the brains of experimental animals used as models of hepatic encephalopathy. Furthermore, this study adds the excitotoxic compound QUIN to the list of molecules possibly involved in the pathogenesis of this brain disorder.

Phenyl-T-Butyl-Nitrone is Active Against Traumatic Shock in Rats

Abstract: Oxygen free-radicals appear to be involved in the pathogenesis of shock; therefore trapping of these radicals would modify the evolution of experimental shock. Experiments were performed on rats submitted to 100% lethal whole body trauma (rotating drum) and their survival, pathology, acid-base status and hematocrit level observed.The spin trapping agent phenyl-t-butyl-nitrone (PBN) was administered before trauma (50, 100, 150 mg/kg i.p.) or at various intervals (30, 60 minutes) after establishment of a severe traumatic shock. It appeared that PBN administration was highly effective both in prevention and in reversion of traumatic shock in rats.

Symptomatic recurrences of carcinoma of the rectum and sigmoid. The influence of radiotherapy on the quality of life.

Abstract: One hundred forty-three patients irradiated for locoregional recurrences after curative surgery for cancer of the rectum and sigmoid were studied retrospectively. An analysis was made of the symptomatic response and survival in the total series and in three subgroups treated with different dose levels (40 Gy or lower, between 40 and 50 Gy, 50 Gy or higher). The symptom-free period was calculated as percent of the overall survival. Symptomatic control was obtained in 80.4 percent of the cases, and the crude patient survival rate was 17.5 percent at two years. No significant difference was found in the three subgroups treated with different dose levels. The cumulative time/patient asymptomatic periods in the total series and in the three subgroups were 31.5, 30.2, 31.8, and 31.9 percent respectively, of the survival period.

Clinical approach to visceral sensation

Abstract: Publisher Summary A common sensation can become clearly unpleasant but not necessarily painful, as in motion sickness or in the sensation of “air hunger”. This chapter discusses the term that defines this kind of unpleasant sensation, “coenaesthesiopathia”. Visceral pain can arise from a visceral common sensation—that is, sensations from the bladder. The common sensation is the feeling of fullness, accompanied by a desire to micturate. If it is inconvenient to micturate, the desire to do so becomes stronger and unpleasant, but it is still not painful. During severe urinary retention, as occurs in acute urinary bladder obstruction, this unpleasant feeling becomes increasingly painful. The most important visceral sensation is the visceral pain. The stimuli that induce pain in viscera are different from those that induce pain in the somatic structures. This explains why in the past the viscera was considered to be insensitive to pain.

Behavioural and ecological adaptations to the high mountain environment of Polistes biglumis bimaculatus

Abstract: . 1 Polistes biglumis bimaculatus (G. in Furcroy) (Hymenoptera: Vespidae), a high mountain species, was studied in the Alps. Adaptations of this species to the severe climate and reduced nesting season include nesting characteristics, social organization and division of labour, and caste succession. 2 Foundress association occurs only in the late pre-emergence period and is not the same as that seen in low altitude species. 3 The foundress females continue to forage even in the post-emergence period and workers and reproductive (males and females) emerge almost contemporaneously.

Cytolytic T lymphocytes with natural killer activity in thyroid infiltrate of patients with Hashimoto's thyroiditis: analysis at clonal level.

Abstract: T Lymphocytes from thyroid infiltrates and peripheral blood (PB) of 3 patients with Hashimoto's thyroiditis (HT) were cloned using a microculture system previously shown to allow the clonal expansion of virtually all PB T lymphocytes from normal individuals. The phenotypic and functional features of a total number of 153 clones from thyroid infiltrates and 206 clones from PB were examined and compared with those of 272 clones derived from normal PB and spleens. The majority of clones derived from thyroid infiltrates of patients with HT had the cytotoxic/suppressor (T8+) phenotype, whereas the majority of clones from PB expressed the helper/inducer (T4+) phenotype. In addition, a consistent proportion (25%) of clones derived from PB of one patient had a phenotype (T3+T4–T8–) that was only occasionally found on clones obtained from PB or spleens of normal subjects. Most clones derived from both PB and thyroid infiltrates of the patients with HT had cytolytic activity, as assessed by a lectin-dependent cytol...

Effect of Adenosine, Adenosine Derivatives, and Caffeine on Acetylcholine Release from Brain Synaptosomes: Interaction with Muscarinic Autoregulatory Mechanisms

Abstract: Synaptosomes, prepared from rat cerebral cortex and hippocampus, were preincubated with [methyl-3H]choline. The effect of adenosine, cyclohexyladenosine, N-ethylcarboxamide adenosine, 2'-deoxyadenosine, and oxotremorine on K+-evoked 3H efflux was investigated. High-voltage electrophoretic separation showed that in the presence of physostigmine, the K+-evoked 3H efflux from hippocampal synaptosomes was 90% [3H]acetylcholine and 10% [3H]choline. Adenosine (30 microM) and oxotremorine (100 microM) both decreased [3H]acetylcholine release from hippocampal synaptosomes. The effect was inversely proportional to the KCl concentration and disappeared at a KCl concentration of 50 mM. Cyclohexyladenosine was approximately 3,000 times more active than adenosine, whereas N-ethylcarboxamide adenosine and 2'-deoxyadenosine were inactive. This indicates that A1 adenosine receptors were involved in the inhibitory effect. Caffeine antagonized the adenosine effect, and at a concentration of 100 microM, it stimulated [3H]acetylcholine efflux. The inhibitory effect of oxotremorine was as great in cortical as in hippocampal synaptosomes. In contrast, adenosine was much less active in cortical than in hippocampal synaptosomes. When inhibitory concentrations of adenosine and oxotremorine were added together into the incubation medium, the effect of adenosine on [3H]acetylcholine release was consistently reduced. An interaction between muscarinic and A1 adenosine presynaptic receptors at a common site modulating acetylcholine release can be assumed.