Showing papers by "University of Palermo published in 1990"

An eclipsing millisecond pulsar in the globular cluster Terzan 5

Abstract: WE HAVE discovered an eclipsing binary millisecond pulsar in the globular cluster Terzan 5. This, the second known eclipsing binary pulsar after PSR1957 + 20, has a pulse period of 11.56 ms and a very short orbital period of 1.8 hours. In contrast to PSR1957 + 20, where the eclipses occupy about 10 per cent of the orbital period1, the eclipse duration in this pulsar is very variable and never less than one-third of the orbital period. The pulsar is in a circular orbit of radius 0.11 light seconds, which implies a minimum companion mass of 0.089 solar masses, about four times the companion mass of PSR1957 + 20. Timing observations suggest an identification of the pulsar with a variable continuum source locate about 30 arcsec west of the cluster centre. These observations and the variable eclipse duration show that the eclipse is due to absorption or scattering in a tenuous wind which flows from the companion star. We have also detected a second pulsar in the direction of Terzan 5. This pulsar, which has a period of 442 ms,may also be a cluster member, but is more likely to be a foreground object.

Rheology-morphology relationships in nylon 6/liquid-crystalline polymer blends

Abstract: Extrusion measurements have been carried out on blends of nylon 6 and a liquid-crystalline copolyesteramide (LCP). The flow curves at low temperature show a behavior similar to that of pure LCP with a rapid rise of the viscosity at low shear rates. At high shear rates the viscosity is lower than that for each of the two components. This minimum has been attributed to the lack of interactions between the two phases and to the formation of fibrils of the LCP phase. The SEM analysis shows, indeed, that fibrils of the LCP phase are produced in the convergent flow at the inlet of the capillary at high shear rates. These fibrils are lost during the flow in the long capillary.

Results of prototype studies for a spaghetti calorimeter

Abstract: In the framework of the LAA project, prototypes for a new type of calorimeter, intended for the detection of both electromagnetic (em) and hadronic showers, muons and missing energy (eg neutrinos) at high-luminosity multi-TeV pp colliders, were tested The detector consists of scintillating plastic fibres embedded in a lead matrix at a volume ratio 1:4, such as to achieve compensation The optimization of the construction of the detector modules is described, as well as the performance concerning em shower and muon detection and e/π separation We used electron, pion and muon beams in the energy range 10–150 GeV for this purpose For the energy resolution of electrons we found 13%/trE, with a constant term of 1% The signal uniformity was better than 3% over the total surface of projective modules The signal linearity for em shower detection was better than 1%, and the e/π separation was better than 5 × 10−4 for isolated particles Channeling effects are negligible, provided that the angle between the incoming particles and the fibre axis is larger than 2°

A breakdown in macromolecular synthesis preceding differentiation in Streptomyces coelicolor A3(2).

Abstract: Summary: A transitory cessation of growth was recorded in Streptomyces coelicolor A3(2) at the end of vegetative mycelium formation on solid medium. In the same phase a striking reduction in protein and nucleic acid synthesis was detected. Growth and macromolecular synthesis resumed, nearly reaching the original values, when morphological differentiation occurred. It is concluded that a physiological stress occurs within the bacterial population just before the onset of the morphological differentiation.

Partial molar volumes and compressibilities of alkyltrimethylammonium bromides

Abstract: Density and ultrasound measurements were performed for dodecyl- and tetradecyltrimethylammonium bromide at 15, 25 and 35°C and for hexadecyltrimethylammonium bromide at 25, 35 and 45°C over a wide concentration region. From these and previously reported data, partial molar volumes and isentropic and isothermal compressibilities were derived as a function of the surfactant concentration. It is shown that by increasing the surfactant concentration the apparent molar volumes and compressibilities increase according to the expected behavior of surfactant solutions. However, anomalies are displayed in plots of apparent molar compressibility of tetradecyltrimethylammonium bromide and of the speed of sound for all the surfactants studied as a function of concentration. These peculiarities can be ascribed to micellar structural transitions. The standard thermodynamic properties and the CH2 group contributions have been obtained by the additivity rule. The results obtained for the compressibility and volume properties are different from those reported in the literature. The volumes and compressibilities of micellization were graphically evaluated on the basis of the pseudo-phase transition model.

Quantitative analysis of ventricular late potentials in healthy subjects.

Abstract: Signal averaging is a technique that improves the signal-to-noise ratio. Obscuring random noise, it allows the detection of low-amplitude wave forms in the terminal portion of the QRS complex, also known as ventricular late potentials. A higher incidence of arrhythmic events has been found in patients with abnormal ventricular late potentials after an acute myocardial infarction. Few studies have been conducted in healthy subjects to assess normal values. Sixty-one healthy subjects were enrolled in our study (33 men and 28 women). The results (mean +/- standard deviation) are as follows: duration of the filtered QRS (QRS duration) was 95 +/- 10 ms; duration of the low-amplitude signals in the terminal portion of QRS less than 40 microV (LAS less than 40) was 32 +/- 8 ms; and root-mean-square voltage in the last 40 ms (RMS - 40) was 33 +/- 16 microV. A significant difference was noted in QRS duration between men and women (98 +/- 11 vs 92 +/- 6 ms, p = 0.006); no difference was found in LAS less than 40 (31 +/- 8 vs 34 +/- 8 ms) and in RMS-40 (36 +/- 17 vs 30 +/- 13 microV). QRS duration confidence limits of 95% were less than or equal to 114 ms for the total group, less than or equal to 120 ms for men and less than or equal to 104 ms for women. Normalization of QRS duration for height (normal value less than 66 ms/m) eliminated any difference between men and women.(ABSTRACT TRUNCATED AT 250 WORDS)

Sparse dynamic programming

Abstract: This paper provides a systematic study of the impact of sparsity on the computation of many different dynamic programming recurrences whose applications include sequence analysis. These recurrences are defined over a number of points that is quadratic in the input size. However, due to natural constraints of the problems, only a sparse set matters for the result. Based on new algorithmic techniques, we obtain algorithms that improve the best known time bounds by a factor almost linear in the density of the problems. All our algorithms are based upon a common unifying methodology.

Capillary experiments of flow induced crystallization of HDPE

Abstract: Flow-induced crystallization experiments are made in a capillary apparatus modified with a downstream reservoir under pressure. Capillary length, diameter, and entrance angle are changed, as well as flow rate. The results show that the crystallization temperature is influenced both by the elongational flow at the capillary entrance and by the shear flow along the capillary. The independent effect of the pressure equals that obtained under static conditions. The effect of shear is correlated in terms of shearing work.

Role of S -Adenosyl-L-Methionine in the Treatment of Intrahepatic Cholestasis

Abstract: Recent studies have established the clinical efficacy of S-adenosyl-L-methionine (SAMe) in the treatment of cholestasis associated with hepatic diseases, pregnancy and the administration of estrogen-containing oral contraceptives. In 4 clinical trials involving a total of 639 patients with cholestasis due to acute or chronic liver disease, SAMe in an intravenous dose of 800 mg/day or an oral regimen of 1.6 g/day for 2 weeks was superior to placebo in relieving the symptom of pruritus and in restoring serum total bilirubin and serum alkaline phosphatase towards normal. The drug is also effective in intrahepatic cholestasis of pregnancy (ICP), with intravenous administration of 800 mg/day for 2 weeks producing a substantial reduction in pruritus and an improvement in abnormal liver function indices. Moreover, SAMe treatment decreases the incidence of premature labour. SAMe appears to be the first safe and effective approach to the treatment of this syndrome, and also protects against the adverse hepatic effects of small doses of estrogen in patients with a history of ICP by normalising liver biochemistry and the oversaturated biliary lipid composition of the gallbladder bile. In animal models, SAMe reverses the pathological liver changes induced by xenobiotics such as taurolithocholate and alpha-naphthyl-isothiocyanate (ANIT) and the antipsychotic chlorpromazine. Several cooperative mechanisms appear to underlie the anticholestatic action of SAMe, the most important being the restoration of normal hepatocyte membrane fluidity and Na+, K+ ATPase activity, through a reversal of the reduction in phospholipid methylation produced by hepatotoxic agents. In addition, SAMe may act by promoting trans-sulphuration pathway reactions and consequently improving the detoxifying capacity of this metabolic system.

The Abbo glossary in London, British Library, Cotton Domitian i

Abstract: The process through which glossaries came into being can sometimes still be seen and studied in surviving manuscripts, and in such cases it provides a valuable index to the way in which Latin texts were studied in medieval schools. This is the case with an unprinted glossary in London, British Library, Cotton Domitian i. The glossary is mainly made up of words taken from bk III of the Bella Parisiacae urbis by Abbo of Saint-Germain-des-Pres, a work which was widely studied in English schools in the tenth and eleventh centuries, above all because of its unusual vocabulary. We know that Abbo drew the unusual vocabulary in his poem from pre-existing glossaries such as the Liber glossarum and the Scholica graecarum glossarum; but he also took from these works the interlinear glosses which he provided for the difficult words in bk III of his poem, and these in turn are found, with little variation, in all of the manuscripts which preserve the poem. Now under the rubric ‘Incipiunt glossae diversae’ in Cotton Domitian i are collected some two hundred lemmata from bk III of the poem, followed in each case by one or more glosses; on examination these glosses are found to be identical with those which accompany the text in other manuscripts. The glossary in Domitian i thus provides a working model of how a glossary was compiled, and is a further witness to the popularity of Abbo's poem in Anglo-Saxon England.

Blends of nylon 6 with a polyethylene functionalized by photooxidation

Abstract: An easy and cheap method to prepare functionalized polyethylene is reported in which polyethylene is photooxidized and then melt-blended with nylon. Structural, rheological, and mechanical modifications indicate that carbonyl, formed during photooxidation, and amine groups react giving rise to copolymers which stabilize the blends. Photooxidized polyethylene from waste could be very effective in preparing polyethylene/polyamide blends with improved properties. This new approach improves over current methods in which compatibilization of polyolefines and polyamides is mostly performed by reacting functionalized polyolefines with polyamides in molten state. The functionalization is achieved by chemical modification of the polyolefines chains. This step could be very expensive.

Xanthogranulomatous Cholecystitis: Histopathological Study and Classification

Abstract: Summary Xanthogranulomatous cholecystitis (XC) is a chronic inflammatory lesion of the gallbladder histologically characterized by the presence of varying amounts of foamy histiocytes in the inflammatory infiltrate. In this study a review of 63 cases selected from 1207 surgically removed gallbladders is presented; the percentage found (5.2%) is slightly higher than that of previous reports showing that XC is less uncommon than generally believed. A detailed microscopic study is performed: the authors observed according to the histological features particularly the different patterns of distribution of the inflammatory infiltrate and postulate the existence of three subtypes of XC: multinodular, focal and diffuse XC. Finally, the main etiopathogenetic hypotheses are briefly discussed.

Partial algebras of closable operators: Part I, the basic theory and the Abelian case

Abstract: This paper, the first of two, is devoted to a systematic study of partial *-algebras of closable operators in a Hilbert space (partial Op*-algebras). After setting up the basic definitions, we describe canonical extensions of partial Op*-algebras by closure and introduce a new bounded commutant, called quasi-weak. We initiate a theory of abelian partial *-algebras. As an application, we analyze thoroughly the partial Op*-algebras generated by a single closed symmetric operator.

Prevalence of human rotavirus serotypes in some European countries 1981-1988.

Abstract: An extended epidemiological survey on the circulation of the 4 established human rotavirus (HRV) serotypes in some European countries was carreid out on 831 fecal strains collected from infants and young children with acute non-bacterial gastroenteritis during 1981–88. Typing was done by enzyme-linked immunosorbent assay and/or solid-phase immune electron microscopy using VW type-specific neutralizing monoclonal antibodies. Serotype 1 HRV strains were found to be largely predominant in this period both in Italy and other countries, whereas serotype 4 strains were less common. The number of strains of serotypes 1 and 4 circulating in Europe was equivalent only in 1983–84. Serotype 2 strains were significantly represented only in 1981–84, while strains of serotype 3 were nearly absent, since only 8 strains (2 of which belonged to subgroup I) were found during the entire study period. About 10 % of strains could not be typed, while 9 strains exhibited dual VW reactivity and 6 were non-group A HRVs. These epi...

Biological protective substances in Marthasterias glacialis (Asteroidea) epidermal secretion

Abstract: Marthasterias glacialis secretes a watery mucous liquid consisting of 14% carbohydrate and 86% protein. The mucous secretion possesses different biological active molecules responsible for lysozyme-like, protease and haemolytic activities. These substances could constitute a molecular barrier playing a protective role against the penetration by bacteria, fungi and parasites. The secretory apparatus consists of two unicellular glands, a large goblet cell and a granular cell, which open directly into the epidermis.

Self-assembly of a bioelastomeric structure: solution dynamics and the spinodal and coacervation lines.

Abstract: The stability, metastability, and instability regions of aqueous solutions of a representative synthetic bioelastomeric polymer, poly (Val-Pro-Gly-Val-Gly), were determined by a combined use of elastic and quasi-elastic light scattering experiments. The approach followed here offers the attractive advantage of singling out the relevant contributions to the total scattering even in the presence of traces of noninteracting larger sized impurities. Conclusions so reached were checked by means of independent experiments. The present results provide descriptions of the very early events in the physics of bioelastogenesis in terms of general polymer science and phase transitions, and in terms of an unexpected possible functional role of density fluctuations.