An importance sampling algorithm for generating exact eigenstates of the nuclear Hamiltonian

We endow a recently devised algorithm for generating exact eigensolutions of large matrices with an importance sampling, which is in control of the extent and accuracy of the truncation of their dimensions. We made several tests on typical nuclei using a correlated basis obtained from partitioning the shell model space. The sampling so implemented allows not only for a substantial reduction of the shell model space but also for an extrapolation to exact eigenvalues and E2 strengths.Comment: A compressed file composed of a text in latex of 19 pages and 9 figures in p

Insulin-like growth factor-1 is a negative modulator of glucagon secretion

Glucagon secretion involves a combination of paracrine, autocrine, hormonal, and autonomic neural mechanisms. Type 2 diabetes often presents impaired glucagon suppression by insulin and glucose. Insulin-like growth factor-I (IGF-1) has elevated homology with insulin, and regulates pancreatic β-cells insulin secretion. Insulin and IGF-1 receptors share considerable structure homology and function. We hypothesized the existence of a mechanism linking the inhibition of α-cells glucagon secretion to IGF-1. Herein, we evaluated the association between plasma IGF-1 and glucagon levels in 116 nondiabetic adults. After adjusting for age gender and BMI, fasting glucagon levels were positively correlated with 2-h post-load glycaemia, HOMA index and fasting insulin, and were negatively correlated with IGF-1 levels. In a multivariable regression, the variables independently associated to fasting glucagon were circulating IGF-1 levels, HOMA index and BMI, explaining 20.7% variation. To unravel the molecular mechanisms beneath IGF-1 and glucagon association, we investigated whether IGF-1 directly modulates glucagon expression and secretion in an in vitro model of α-cells. Our data showed that IGF-1 inhibits the ability of low glucose concentration to stimulate glucagon expression and secretion via activation of the phosphatidylinositol-3-kinase/Akt/FoxO1 pathway. Collectively, our results suggest a new regulatory role of IGF-1 on α-cells biological function

Plasma kisspeptin levels are associated with insulin secretion in nondiabetic individuals

To evaluate if plasma kisspeptin concentrations are associated with insulin secretion, as suggested by recent in vitro studies, independently of confounders. 261 nondiabetic subjects were stratified into tertiles according to kisspeptin values. Insulin secretion was assessed using indexes derived from oral glucose tolerance test (OGTT). After adjusting for age, gender, and BMI, subjects in the highest (tertile 3) kisspeptin group exhibited significantly lower values of insulinogenic index, corrected insulin response (CIR30), and Stumvoll indexes for first-phase and second-phase insulin release as compared with low (tertile 1) or intermediate (tertile 2) kisspeptin groups. Univariate correlations between kisspeptin concentration and metabolic variables showed that kisspeptin concentration was significantly and positively correlated with age, blood pressure, and 2-h post-load glucose, and inversely correlated with BMI, and waist circumference. There was an inverse relationship between kisspeptin levels and OGTT-derived indexes of glucose-stimulated insulin secretion. A multivariable regression analysis in a model including all the variables significantly correlated with kisspeptin concentration showed thar age (β = -0.338, P<0.0001), BMI (β = 0.272, P<0.0001), 2-h post-load glucose (β = -0.229, P<0.0001), and kisspeptin (β = -0.105, P = 0.03) remained associated with insulinogenic index. These factors explained 34.6% of the variance of the insulinogenic index. In conclusion, kisspeptin concentrations are associated with insulin secretion independently of important determinants of glucose homeostasis such as gender, age, adiposity, 2-h post-load glucose, and insulin sensitivity

Solution of large scale nuclear structure problems by wave function factorization

Low-lying shell model states may be approximated accurately by a sum over products of proton and neutron states. The optimal factors are determined by a variational principle and result from the solution of rather low-dimensional eigenvalue problems. Application of this method to sd-shell nuclei, pf-shell nuclei, and to no-core shell model problems shows that very accurate approximations to the exact solutions may be obtained. Their energies, quantum numbers and overlaps with exact eigenstates converge exponentially fast as the number of retained factors is increased.Comment: 12 pages, 12 figures (from 15 eps files) include

Proton-Neutron Interaction near Closed Shells

Odd-odd nuclei around double shell closures are a direct source of information on the proton-neutron interaction between valence nucleons. We have performed shell-model calculations for doubly odd nuclei close to $^{208}$Pb, $^{132}$Sn and $^{100}$Sn using realistic effective interactions derived from the CD-Bonn nucleon-nucleon potential. The calculated results are compared with the available experimental data, attention being focused on particle-hole and particle-particle multiplets. While a good agreement is obtained for all the nuclei considered, a detailed analysis of the matrix elements of the effective interaction shows that a stronger core-polarization contribution seems to be needed in the particle-particle case.Comment: 8 pages, 6 figures, Proccedings of the International Conference "Nuclear Structure and Related Topics", Dubna, Russia, September 2-6, 2003, to be published in Yadernaia Fizika (Physics of Atomic Nuclei

Association between serum Mg2+ concentrations and cardiovascular organ damage in a cohort of adult subjects

Magnesium (Mg2+) levels are associated with insulin resistance, hypertension, atherosclerosis, and type 2 diabetes (T2DM). We evaluated the clinical utility of physiological Mg2+ in assessing subclinical cardiovascular organ damage including increased carotid artery intima-media thickness (c-IMT) and left ventricular mass index (LVMI) in a cohort of well-characterized adult non-diabetic individuals. Age-and gender-adjusted correlations between Mg2+ and metabolic parameters showed that Mg2+ circulating levels were correlated negatively with body mass index (BMI), fasting glucose, and 2h-oral glucose tolerance test (OGTT) glucose. Similarly, Mg2+ levels were significantly and negatively related to c-IMT and LVMI. A multivariate regression analysis revealed that age (β = 0.440; p < 0.0001), BMI (β = 0.225; p < 0.0001), and Mg2+ concentration (β = −0.122; p < 0.01) were independently associated with c-IMT. Age (β = 0.244; p = 0.012), Mg2+ (β = −0.177; p = 0.019), and diastolic blood pressure (β = 0.184; p = 0.038) were significantly associated with LVMI in women, while age (β = 0.211; p = 0.019), Mg2+ (β = −0.171; p = 0.038) and the homeostasis model assessment index of insulin resistance (HOMA-IR) (β = −0.211; p = 0.041) were the sole variables associated with LVMI in men. In conclusion, our data support the hypothesis that the assessment of Mg2+ as part of the initial work-up might help unravel the presence of subclinical organ damage in subjects at increased risk of cardiovascular complications

Complete breakdown of the Debye model of rotational relaxation near the isotropic-nematic phase boundary: Effects of intermolecular correlations in orientational dynamics

The Debye-Stokes-Einstein (DSE) model of rotational diffusion predicts that the rotational correlation times $\tau_{l}$ vary as $[l(l+1)]^{-1}$, where $l$ is the rank of the orientational correlation function (given in terms of the Legendre polynomial of rank $l$). One often finds significant deviation from this prediction, in either direction. In supercooled molecular liquids where the ratio $\tau_{1}/\tau_{2}$ falls considerably below three (the Debye limit), one usually invokes a jump diffusion model to explain the approach of the ratio $\tau_{1}/\tau_{2}$ to unity. Here we show in a computer simulation study of a standard model system for thermotropic liquid crystals that this ratio becomes much less than unity as the isotropic-nematic phase boundary is approached from the isotropic side. Simultaneously, the ratio $\tau_2/\eta$ (where $\eta$ is the shear viscosity of the liquid) becomes {\it much larger} than hydrodynamic value near the I-N transition. We have also analyzed the break down of the Debye model of rotational diffusion in ratios of higher order rotational correlation times. We show that the break down of the DSE model is due to the growth of orientational pair correlation and provide a mode coupling theory analysis to explain the results.Comment: Submitted to Physical Review

INTRA-DUODENAL RELEASE OF A BITTER COMPOUND DECREASES CALORIC INTAKE IN HEALTHY VOLUNTEERS

Background and aim: α-gustducin and bitter taste receptors (T2R) are expressed both in the oral cavity and in the gastrointestinal (GI) tract. Experimental data showed that bitter tastants induce the release of gut hormones from enteroendocrine cells in the gut, suggesting a possible role of bitter taste receptors in the control of food intake and GI functions. We aimed to test the effects of a bitter taste receptor agonist on food intake and GI feelings. Material and methods: We enrolled 19 healthy subjects (9 males, age 27±7, BMI 24±6) in a double-blind placebo controlled study. Each subject randomly received an acid-resistant capsule containing placebo or 18 mg of quinine HCl. 60 minutes after capsule administration, the subjects underwent to an ad libitum test, until the maximum satiation. Meal test was composed by white bread, cheese and meat cream (89 kcal/portion: 50% carbohydrate, 31% fat, 19% protein). Caloric intake, meal duration and satiation levels, scored on a Visual Analogue Scale (VAS) were calculated at the end of the meal test. A questionnaire assessing GI sensations (bloating, fullness, nausea, epigastric discomfort and hunger) was administered before and at the end of the test. Data (mean ± SD) were compared by using paired t test. Results: No oral bitter sensation or side effects was observed both with quinine HCland placebo. No significant differences in terms of GI sensations and hunger feelings were observed between the two sessions of the study. The amount of calories ingested was significantly lower when subjects received quinine HCl than placebo (564±262 vs 667±278 kcal; p=0.02). Conversely, quinine HCl did not affect the meal duration (14.4±4.2 vs 16.6±4.6 min; p=NS) and the satiationintensity (82 vs 82 mm; p=NS). Conclusions: The intra-duodenal release of a bitter compound significantly decreases caloric intake in an ad libitum test meal without affecting GI sensations and hunger feeling. As the bitter compound does not influence meal duration, we hypothesize that quinine HCl decreases the caloric intake by affecting the rate of meal portions consumption. Evaluation of gut hormones kinetics and studies with other bitter taste receptor agonist are needed to establish the role of gastrointestinal bitter taste receptor in the control of food intak

Bonn Potential and Shell-Model Calculations for 206,205,204Pb

The structure of the nuclei 206,205,204Pb is studied interms of shell model employing a realistic effective interaction derived from the Bonn A nucleon-nucleon potential. The energy spectra, binding energies and electromagnetic properties are calculated and compared with experiment. A very good overall agreement is obtained. This evidences the reliability of our realistic effective interaction and encourages use of modern realistic potentials in shell-model calculations for heavy-mass nuclei.Comment: 4 pages, 4 figures, submitted to Physical Review

Variações Longitudinais de Lipoproteínas de Baixa Densidade Oxidadas Associadas à Artéria "Culpada" no Enfarte do Miocárdio com Elevação ST - um Marcador Promissor?

The aim of the present study was to investigate variations in oxidized LDL (oxLDL) at the onset of acute myocardial infarction (AMI) and over the recovery period, exploring their relationship with coronary disease severity. A follow-up of 50 AMI patients was evaluated against 25 healthy volunteers (reference group). The AMI patients were evaluated at three time points: at admission before the administration of IIb/IIIa inhibitors and angioplasty, and two and 40 days after intervention. Plasma oxLDL concentrations were measured by ELISA. oxLDL was found to be significantly higher in AMI patients in the acute phase relative to reference levels, decreasing progressively over the recovery period. The results also demonstrated that oxLDL levels were decreased in patients with the left circumflex artery (LCX) as culprit vessel compared to the left anterior descending coronary (LAD) or right coronary artery (RCA). The results highlight a significant increase in oxLDL concentration related to coronary artery disease severity, as conditions such as LCX lesions are usually associated with a favorable prognosis, contrasting with LAD-associated conditions that can compromise large areas of myocardium. The results thus suggest that oxLDL may constitute a promising marker in assessment of AMI evolution