Paolo Ventura

We adopt up-to-date 7Li yields from asymp- totic giant branch stars in order to study the temporal evolution of 7Li in the solar neighbourhood in the context of a revised version of the two-infall model for the chemical evolution of our galaxy. We consider several lithium stellar sources besides the asymptotic giant branch stars such as Type II supernovae, novae,

Horizontal branch stars belong to an advanced stage in the evolution of the oldest stellar galactic population, occurring either as field halo stars or grouped in globular clusters. The discovery of multiple populations in clusters that were previously believed to have single populations gave rise to the currently accepted theory that the hottest horizontal branch members (the 'blue hook' stars, which had late helium-core flash ignition, followed by deep mixing) are the progeny of a helium-rich 'second generation' of stars. It is not known why such a supposedly rare event (a late flash followed by mixing) is so common that the blue hook of ω Centauri contains approximately 30 per cent of the horizontal branch stars in the cluster, or why the blue hook luminosity range in this massive cluster cannot be reproduced by models. Here we report that the presence of helium core masses up to about 0.04 solar masses larger than the core mass resulting from evolution is required to solve the luminosity range problem. We model this by taking into account the dispersion in rotation rates achieved by the progenitors, whose pre-main-sequence accretion disk suffered an early disruption in the dense environment of the cluster's central regions, where second-generation stars form. Rotation may also account for frequent late-flash-mixing events in massive globular clusters.

We present the results of stellar evolutionary computations to study the sensitivity of lithium depletion in models of mass and metallicity close to solar, and its dependence on the micro - macro physical inputs in the models, like thermodynamics, mixing, overshooting and the convective model. We find that even marginal chemical inhomogeneities in stellar formation regions lead to a spread

ABSTRACT In 1965 Edmonds gave the first complete polyhedral description for a combinatorial optimization problem: the Matching polytope. Many researchers tried to generalize his result by considering the Stable Set polytope of claw-free graphs. However this is still an open problem. Here we solve it for the class of claw-free graphs with stability number greater than 3 and without 1-joins.

ABSTRACT We define the class of geared (fuzzy) line graphs as the class of graphs obtained by repeated applications of the extended gear composition to a (fuzzy) line graph H. Using the decomposition theorem for claw-free graphs of Chudnovsky and Seymour [2], we show that this class represents a large subclass of claw-free graphs having stability number at least 4. We provide a complete linear description of the stable set polytope of geared (fuzzy) line graphs. This result gives a first substantial answer to the longstanding open question of finding a defining linear system for the stable set polytope of claw-free graphs [10].

NGC 2808 is one of the globular clusters containing multiple stellar populations in our Galaxy. The cluster color-magnitude diagram contains two extra sequences blueward of the main cluster ridge-line. Stars on these sequences appear to be enhanced in Helium up to Y=0.40. The origin of these stars is still mysterious although they are believed to be produced from the ejecta

We continue our study of rich Galactic clusters by presenting deep CCD observations of both NGC 2168 (M35) and NGC 2323 (M50). Both clusters are found to be rich (NGC 2168 contains at least 1000 stars brighter than V = 22 and NGC 2323 contains approximately 2100 stars brighter than our photometric limit of V = 23) and young (age

We present theoretical mass-luminosity relations and luminosity functions (LFs) for globular cluster stars, from luminosities above the horizontal branch down to the minimum luminosity of hydrogen-burning stars. The LFs are available for metal mass fraction Z from Z= 10-4 to ...

... Francesca D'Antona and Paolo Ventura Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone, Italy; dantona@coma.mporzio.astro.it ... Both the strong X-ray emission, attributed to the corona activated by the presence of a magnetic field, and the recent ...

Acute administration of N-acetylcysteine (NAC) may induce alterations in plasma and urinary levels of homocysteine (Hcy) and cysteine (Cys). We studied the effects of continuous oral NAC therapy on different Hcy and Cys plasma and urinary forms in 40 healthy subjects assigned to three groups (groups A: n = 13, no therapy; group B: n = 14, NAC 600 mg/day, and group C: n = 14, NAC 1,800 mg/day) for 1 month (T(1)). After a 1-month washout period without therapy (T(2)), all subjects were treated with oral NAC (1,800 mg/day) for 2 months and (T(3) and T(4)) reassessed monthly for plasma and urinary thiols. The treated subjects showed a significant decrease in plasma total Hcy and a slight increase in total Cys levels; the alterations of different forms of plasma thiols suggested an NAC-induced increase in disulfide forms and an increase in urinary Hcy and Cys excretion as disulfide forms. The effects appeared to be dose dependent, being more marked in subjects treated with higher dosages. This approach may be important, as an association or alternative therapy in hyperhomocysteinemic conditions of poor responses to vitamins.

Hyperhomocysteinemia (HHcy) is a metabolic disorder frequently occurring in the elderly population. Recently several reports have suggested abnormalities in homocysteine (tHcy) metabolism implicating HHcy as a metabolic link in the multifactorial processes characterizing many geriatric illnesses-with special emphasis on atherosclerotic vascular diseases and cognitive impairment. The present study was undertaken in a large sample of elderly hospitalized subjects to determine (1) the prevalence of HHcy, (2) the association of HHcy with vascular and cognitive disorders, and (3) the factors independently predicting Hhcy. Six hundred elderly subjects (264 men and 336 women; mean age, 79 +/- 9 years) were randomly chosen from those admitted as inpatients over a period of 3 years. In all patients, body mass index (BMI), mid-upper arm muscle area (MUAMA), plasma cholesterol, triglycerides, total proteins, albumin, lymphocyte count, creatinine, homocysteine (fasting and 4 hours after methionine oral load), serum vitamin B(6), vitamin B(12), and folate concentrations were measured. The presence of disease or use of medications known to affect homocysteine plasma levels were also recorded. The mean fasting tHcy level was 16.8 +/- 12 micromol/L in the whole sample, 18.18 +/- 13.25 micromol/L in men, and 15.86 +/- 12.14 micromol/L in women (P =.005 men v women). The mean Hcy level 4 hours after methionine load was 37.95 +/- 20.9 in the whole sample. Prevalence of hyperhomocysteinemia (fasting Hcy > or = 15 micromol/L or 4 hours after methionine load > or = 35 micromol/L) was 61% (365/600) (67% in men and 56% in women, P <.05). HHcy was rarely (8%) an isolated disorder; in addition to diabetes (20%), renal failure (48.2%), and malnutrition (20.2%), it was often associated with heart failure (30%), malignancies (20.5%), and the use of diuretics (56%) and anticonvulsant drugs (13%). Plasma homocysteine progressively increases across subjects from those with no diabetes, malnutrition, renal failure, obesity, inflammatory bowel disease, heart failure to those with 1, 2, or more concurrent diseases. Multiple stepwise regression analysis showed that 72% of plasma total fasting tHcy variability was explained by age, serum folate, plasma albumin, use of diuretics, and renal function (measured as plasma creatinine clearance). In conclusion, the present study documents that hyperhomocysteinemia, in elderly hospitalized patients is (1) a common finding, (2) frequently associated with vascular and cognitive disorders, and (3) probably a secondary phenomenon in most cases. The major predictor of high plasma homocysteine levels were age, serum folate, plasma albumin, plasma creatinine clearance, and use of diuretic drugs. These variables explain a large proportion of plasma Hcy variability.

Hyperhomocysteinemia is a risk factor for vascular disease, although its mechanism of action is not fully clear. Different experimental studies have suggested that homocysteine (Hcy) exerts a pro-oxidant effect in the presence of metal ions (Fe and Cu). To test for a similar effect in vivo, we studied plasma markers of lipid and protein oxidation during hyperhomocysteinemia induced by an oral methionine load. Twenty-nine subjects (aged 61 +/- 25 years; 17 women), 25 of whom underwent oral methionine (100 mg/kg) loading, were studied; in every case, we measured total plasma Hcy, malondialdehyde (MDA), conjugated dienes (DIE), and oxidized protein ([PTOX] carbonylic groups) in basal conditions and 4, 6, 8, and 24 hours after methionine loading. Four participants acted as controls. In every case, we also measured total plasma antioxidant capacity (ANTOX) in basal conditions and 8 hours after methionine loading. Eight hours after methionine loading, plasma Hcy increased from 17.6 +/- 11.4 to 54.3 +/- 31.6 nmol/mL, PTOX from 0.33 +/- 0.18 to 0.71 +/- 0.33 nmol/mg protein, DIE from 493 +/- 163 to 590 +/-202 optical density units, and MDA from 1.66 +/- 0.81 to 2.1 +/- 0.93 nmol/mL. There was a significant correlation (Spearman's r) between Hcy and both PTOX (r = .86, P = .01) and MDA (r = .47, P < .05) 8 hours after methionine loading. No significant modifications of the plasma parameters were found during the observation period in controls. ANTOX at 8 hours was significantly (paired ttest) reduced in probands (from 1.74 +/- 0.59 to 1.14 +/- 0.55 mmol/mL, P = .014); no significant difference was observed for plasma ANTOX in controls. Hyperhomocysteinemia due to oral methionine loading induced an increase in plasma oxidation markers. In the absence of hyperhomocysteinemia, no significant modifications were observed. These findings, together with the decrease in ANTOX and the corresponding increase in total plasma Hcy, are consistent with a pro-oxidant effect of acute hyperhomocysteinemia in vivo.

To evaluate the effect of a continuous combined oral hormone replacement therapy (HRT) on basal and post-methionine load homocysteine levels in postmenopausal women. Twenty-two postmenopausal women (PMW) were randomly allocated to receive either continuous combined oral HRT (2 mg of estradiol plus 1 mg of norethisterone acetate; n = 11) or no treatment (controls, n = 11) for 6 months. A methionine oral load (0.1 g/kg body weight) was performed in each subject at time 0 and after 6 months. Serum homocysteine levels were measured by high-performance liquid chromatography in samples collected at time 0 and at 4, 8, and 24 h after the methionine load, while levels of vitamin B6 (by high-performance liquid chromatography) and B12 and folate (both by ELISA) were assayed in samples collected at time 0. Serum levels of glucose and body mass index increased in treated PMW, whereas folate decreased in controls. In treated PMW, basal homocysteine tended to decrease (10.6 +/- 3.3 micromol/L vs. 9.62 +/- 2.8 micromol/L, p = 0.062), whereas in controls it significantly increased (10.7 +/- 2.65 micromol/L vs. 12.17 +/- 3.89 micromol/L, p < 0.05). This increase was not significant after correction for vitamin status (p = 0.072). Homocysteine values 4 h (31.9 +/- 13.53 micromol/L vs. 39.83 +/- 22.53 micromol/L, p < 0.05) and 8 h (35.1 +/- 13.13 vs. 43.34 +/- 22.15 micromol/L) after methionine, and integrated homocysteine response to methionine (392.5 +/- 133.8 micromol/24 h vs. 458.8 +/- 104.8 micromol/24 h; p < 0.05), were significantly reduced in HRT-treated, but not in untreated, PMW. Continuous combined oral HRT with17beta-estradiol plus norethisterone acetate reduces homocysteine levels, mainly after a methionine load. This effect seems to be independent of vitamin status and may have positive implications for the prevention of cardiovascular diseases in PMW.

ABSTRACT Graphs obtained by applying the gear composition to a given graph H are called geared graphs. We show how a linear description of the stable set polytope STAB(G) of a geared graph G can be obtained by extending the linear inequalities defining STAB(H) and STAB(He), where He is the graph obtained from H by subdividing the edge e. We also introduce the class of G-perfect graphs, i.e., graphs whose stable set polytope is described by nonnegativity inequalities, rank inequalities, lifted 5-wheel inequalities, and some special inequalities called geared inequalities and g-lifted inequalities. We prove that graphs obtained by repeated applications of the gear composition to a given graph H are G-perfect, provided that any graph obtained from H by subdividing a subset of its simplicial edges is G-perfect. In particular, we show that a large subclass of claw-free graphs is G-perfect.

ABSTRACT Complexation of ursodeoxycholic acid (UDCA) with 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) improves the water solubility and the dissolution rate of UDCA and may therefore increase its bioavailability. We compared the amount and the rate of biliary excretion of UDCA and biliary lipid secretion after a single oral administration of UDCA in 3 different pharmaceutical formulations [UDCA-HPbetaCD ('urso-beta-cyclodextrin'), UDCA suspension and UDCA capsule] at 3 different dosages each, in 11 groups (2 control groups) of bile fistula rats. UDCA excretion increased with an increase in dose, biliary UDCA recovery and peak secretion were significantly higher after administration of UDCA-HPbetaCD than after UDCA in suspension or capsule. This enhancement of biliary excretion may achieve greater UDCA enrichment in the bile acid pool than conventional pharmaceutical UDCA formulations, this giving to UDCA-HPbetaCD a considerable therapeutical potential.

Sixteen patients (15 males, aged 48-70) affected by liver cirrhosis and oesophageal varices were subjected to duplex-Doppler ultrasonographic study (DDUS). Four patients (three with a portal thrombosis and one with a hepatofugal portal flow) were excluded from the subsequent pharmacological test. The twelve remaining patients took part in a double blind cross-over study that evaluated the variations of heart rate (HR), mean systemic arterial pressure (SAP), portal vein diameter (PVD), maximal and mean portal flow velocity (PFV) after the administration of either 40 mg of propranolol or placebo per os, on two consecutive days. Propranolol caused no significant variation in mean SAP and in PVD, whereas it reduced the HR from 67.7 +/- 8.0 to 58.4 +/- 7.0 beats/min (mean +/- s.d.; P less than 0.001); the maxPFV dropped from 18.2 +/- 5.4 to 14.0 +/- 3.7 cm/s (P less than 0.001) and the meanPFV dropped from 15.3 +/- 4.1 to 13.2 +/- 3.1 cm/s (P less than 0.005). No significant variation was observed with placebo. After propranolol administration eight patients exhibited a significant maxPFV decrease, whereas the other four patients exhibited only a drop in HR, suggesting either drug inefficacy, inappropriate dosage or inadequate duration of treatment. DDUS is the only non-invasive method for the examination of the portal vein system.(ABSTRACT TRUNCATED AT 250 WORDS)

Portal venous flow velocity (PFV) was measured with duplex-Doppler equipment in 50 normal subjects and in 117 patients with suspected chronic liver disease who showed no evidence of decompensation such as ascites, hepatic encephalopathy, jaundice or oesophageal bleeding. All the patients underwent percutaneous liver biopsy which demonstrated non-cirrhotic liver disease in 58 cases (CH-patients: steatosis 8, persistent chronic hepatitis 8, active chronic hepatitis 42) and liver cirrhosis in the other 59 cases (LC-patients). The normal subjects and the CH-patients had similar values of max-PFV and mean-PFV (max-PFV 26.7 +/- 3.2 and 25.7 +/- 3.4 cm/s respectively; mean-PFV 22.9 +/- 2.8 and 22.4 +/- 3.8 cm/s respectively). The LC-patients' values (max-PFV 19.3 +/- 3.5; mean-PFV 16.9 +/- 2.9) were significantly lower than those of the normal subjects (P less than 0.001) and of the CH-patients (P less than 0.001). Considering the normal max-PFV to be in the range 20-33.1 cm/s (mean +/- 2 s.d. of the normal subjects, 95% confidence limits), max-PFV was reduced in 0/50 normal subjects, 1/58 CH-patients and 39/59 LC-patients (66.1% sensitivity; 98.2% specificity). In conclusion, the duplex-Doppler measurement of PFV is of great interest in the diagnostic study of patients with suspected chronic compensated liver disease and in the early diagnosis of cirrhosis. A low max-PFV is a reliable pointer to liver cirrhosis, whereas a normal max-PFV indicates a non-cirrhotic liver disease but is less probative. Each centre should standardize normal PFV values in order to establish their own threshold value for diagnosing liver cirrhosis.

ABSTRACT In [6], Edmonds provided the first complete description of the polyhedron associated with a combinatorial optimization problem: the matching polytope. As the matching problem is equivalent to the stable set problem on line graphs, many researchers tried to generalize Edmonds' result by considering the stable set problem on a superclass of line graphs: the claw-free graphs. However, as testified also by Grötschel, Lovász, and Schrijver [14], “in spite of considerable efforts, no decent system of inequalities describing STAB(G)STAB(G)for claw-free graphs is known”. Here, we provide an explicit linear description of the stable set polytope of claw-free graphs with stability number at least four and with no 1-join.

In many applications, a sequencing of patterns (electronic circuit nodes, cutting patterns, product orders, etc.) has to be found in order to optimize some given objective function, giving rise to the so-called open stack problems. We focus on a problem related to the optimization of gate matrix layouts: electronic circuits are obtained by connecting gates and one seeks a gate

ABSTRACT In this paper we give an explicit description of the stable set polytope of a claw-free graph obtained by repeated applications of the strip composition of fuzzy linear interval strips, fuzzy XX-strips, and fuzzy antihat strips. Using a decomposition theorem of Chudnovsky and Seymour, this allows us to describe the stable set polytope of all facet defining claw-free graphs with stability number greater than 3.

ABSTRACT The 22-bond is a generalization of the 22-join where the subsets of nodes that are connected on each shore of the partition are not necessarily disjoint. If all the subsets are cliques we say that the 2-bond is a 22-clique-bond.The 22-clique-bond composition builds a graph GG admitting a 2-clique-bond starting from two graphs G1G1 and G2G2. We prove that a linear description of the stable set polytope of GG is obtained by properly composing the linear inequalities describing the stable set polytopes of G1G1, G2G2 and two other related graphs.We explain how to apply iteratively the 22-clique-bond composition to provide the complete linear description of the stable set polytope of new classes of graphs.