The impact of systematic uncertainties in stellar parameters on integrated spectra of stellar populations

In this paper we investigate a hitherto unexplored source of potentially significant error in stellar population synthesis (SPS) models, caused by systematic uncertainties associated with the three fundamental stellar atmospheric parameters; effective temperature T_eff, surface gravity g, and iron abundance [Fe/H]. All SPS models rely on calibrations of T_eff, logg and [Fe/H] scales, which are implicit in stellar models, isochrones and synthetic spectra, and are explicitly adopted for empirical spectral libraries. We assess the effect of a mismatch in scales between isochrones and spectral libraries (the two key components of SPS models) and quantify the effects on 23 commonly used diagnostic line indices. We find that typical systematic offsets of 100K in T_eff, 0.15 dex in [Fe/H] and/or 0.25 dex in logg significantly alter inferred absolute ages of simple stellar populations (SSPs) and that in some circumstances, relative ages also change. Offsets in T_eff, logg and [Fe/H] scales for a scaled-solar SSP produce deviations from the model which can mimic the effects of altering abundance ratios to non-scaled-solar chemical compositions, and could also be spuriously interpreted as evidence for a more complex population, especially when multiple-index or full-SED fitting methods are used. We stress that the behavior we find can potentially affect any SPS models, whether using full integrated spectra or fitting functions to determine line strengths. We present measured offsets in 23 diagnostic line indices and urge caution in the over-interpretation of line-index data for stellar populations.Comment: 14 pages, including 4 figures and 3 tables. Accepted for publication in Ap

A large stellar evolution database for population synthesis studies. IV. Integrated properties and spectra

This paper is the 4th in a series describing the latest additions to the BaSTI stellar evolution database, which consists of a large set of homogeneous models and tools for population synthesis studies. Here we present a new set of low and high resolution synthetic spectra based on the BaSTI stellar models, covering a large range of simple stellar populations (SSPs) for both scaled solar and alpha-enhanced metal mixtures. This enables a completely consistent study of the photometric and spectroscopic properties of both resolved and unresolved stellar populations, and allows us to make detailed tests on their integrated properties. Our low resolution spectra are suitable for deriving broadband magnitudes and colors in any photometric system. These spectra cover the full wavelength range (9-160000nm) and include all evolutionary stages up to the end of AGB evolution. Our high resolution spectra are suitable for studying the behaviour of line indices and we have tested them against a large sample of Galactic globular clusters. We find that the range of ages, iron abundances [Fe/H], and degree of alpha-enhancement predicted by the models matches observed values very well. We have also tested the global consistency of the BaSTI models by making detailed comparisons between ages and metallicities derived from isochrone fitting to observed CMDs, and from line index strengths, for the Galactic globular cluster 47Tuc and the open cluster M67. For 47Tuc we find reasonable agreement between the 2 methods, within the estimated errors. From the comparison with M67 we find non-negligible effects on derived line indices caused by statistical fluctuations, which are a result of the specific method used to populate an isochrone and assign appropriate spectra to individual stars. (abridged)Comment: 21 pages including 13 figures. Accepted for publication in ApJ. Low and high resolution integrated spectra, magnitudes, and mass-to-light ratios will appear on the BaSTI website by 1st November 2008 - see http://193.204.1.62/index.htm

Risk of sports: do we need a pre-participation screening for competitive and leisure athletes?

Sudden cardiac arrest is most often the first clinical manifestation of an underlying cardiovascular disease and usually occurs in previously asymptomatic athletes. The risk benefit ratio of physical exercise differs between young competitive athletes and middle-age/senior individuals engaged in leisure-time sports activity. Competitive sports are associated with an increase in the risk of sudden cardiovascular death (SCD) in susceptible adolescents and young adults with underlying cardiovascular disorders. In middle-age/older individuals, physical activity can be regarded as a ‘two-edged sword': vigorous exertion increases the incidence of acute coronary events in those who did not exercise regularly, whereas habitual physical activity reduces the overall risk of myocardial infarction and SCD. Although cardiovascular pre-participation evaluation offers the potential to identify athletes with life-threatening cardiovascular abnormalities before onset of symptoms and may reduce their risk of SCD, there is a significant debate among cardiologists about efficacy, impact of false-positive results and cost-effectiveness of routine screening. This review presents an appraisal of the available data and criticisms concerning screening programmes aimed to prevent SCD of either young competitive athletes or older individuals engaged in leisure-time sports activit

A review of the molecular mechanisms underlying the development and progression of cardiac remodeling

Pathological molecular mechanisms involved in myocardial remodeling contribute to alter the existing structure of the heart, leading to cardiac dysfunction. Among the complex signaling network that characterizes myocardial remodeling, the distinct processes are myocyte loss, cardiac hypertrophy, alteration of extracellular matrix homeostasis, fibrosis, defective autophagy, metabolic abnormalities, and mitochondrial dysfunction. Several pathophysiological stimuli, such as pressure and volume overload, trigger the remodeling cascade, a process that initially confers protection to the heart as a compensatory mechanism. Yet chronic inflammation after myocardial infarction also leads to cardiac remodeling that, when prolonged, leads to heart failure progression. Here we review the molecular pathways involved in cardiac remodeling, with particular emphasis on those associated with myocardial infarction. A better understanding of cell signaling involved in cardiac remodeling may support the development of new therapeutic strategies towards the treatment of heart failure and reduction of cardiac complications. We will also discuss data derived from gene therapy approaches for modulating key mediators of cardiac remodeling

Modelling realistic horizontal branch morphologies and their impact on spectroscopic ages of unresolved stellar systems

The presence of an extended blue horizontal branch (HB) in a stellar population is known to affect the age inferred from spectral fitting to stellar population synthesis models. However, most population synthesis models still rely on theoretical isochrones which do not include realistic modelling of extended HBs. In this work, we create detailed models for a range of old simple stellar populations (SSPs), to create a variety of realistic HB morphologies, from extended red clumps, to extreme blue HBs. We achieve this by utilising stellar tracks from the BaSTI database and implementing a different mass loss prescription for each SSP created, resulting in different HB morphologies. We find that, for each metallicity, there is some HB morphology which maximises Hbeta, making an underlying 14Gyr population look ~5-6Gyr old for the low and intermediate metallicity cases, and as young as 2Gyr for a solar metallicity SSP. We explore whether there are any spectral indices capable of breaking the degeneracy between an old SSP with extended blue HB and a truly young or intermediate age SSP, and find that the CaII index of Rose(1984) and the strength of the MgII doublet at 2800A are promising candidates, in combination with Hbeta and other metallicity indicators such as Mgb and Fe5406. We also run Monte Carlo simulations to investigate the level of statistical fluctuations in the spectra of typical stellar clusters. We find that fluctuations in spectral indices are significant even for average to large globular clusters, and that various spectral indices are affected in different ways, which has implications for full-spectrum fitting methods. Hence we urge caution if these types of stellar clusters are to be used as empirical calibrating objects for various aspects of SPS models. (Abridged)Comment: Accepted for publication in MNRAS. 10 pages, including 7 figure

Ventricular arrhythmias in young competitive athletes: Prevalence, determinants, and underlying substrate

Whether ventricular arrhythmias (VAs) represent a feature of the adaptive changes of the athlete's heart remains elusive. We aimed to assess the prevalence, determinants, and underlying substrates of VAs in young competitive athletes.Background--Whether ventricular arrhythmias (VAs) represent a feature of the adaptive changes of the athlete's heart remains elusive. We aimed to assess the prevalence, determinants, and underlying substrates of VAs in young competitive athletes. Method and Results--We studied 288 competitive athletes (age range, 16-35 years; median age, 21 years) and 144 sedentary individuals matched for age and sex who underwent 12-lead 24-hour ambulatory electrocardiographic monitoring. VAs were evaluated in terms of number, complexity (ie, couplet, triplet, or nonsustained ventricular tachycardia), exercise inducibility, and morphologic features. Twenty-eight athletes (10%) and 13 sedentary individuals (11%) showed > 10 isolated premature ventricular beats (PVBs) or 651 complex VA (P=0.81). Athletes with > 10 isolated PVBs or 651 complex VA were older (median age, 26 versus 20 years; P=0.008) but did not differ with regard to type of sport, hours of training, and years of activity compared with the remaining athletes. All athletes with > 10 isolated PVBs or 651 complex VA had a normal echocardiographic examination; 17 of them showing > 500 isolated PVBs, exercise-induced PVBs, and/or complex VA underwent additional cardiac magnetic resonance, which demonstrated nonischemic left ventricular late gadolinium enhancement in 3 athletes with right bundle branch block PVBs morphologic features. Conclusions--The prevalence of > 10 isolated PVBs or 651 complex VA at 24-hour ambulatory electrocardiographic monitoring did not differ between young competitive athletes and sedentary individuals and was unrelated to type, intensity, and years of sports practice. An underlying myocardial substrate was uncommon and distinctively associated with right bundle branch block VA morphologic features

Direct 16S rRNA-seq from bacterial communities: a PCR-independent approach to simultaneously assess microbial diversity and functional activity potential of each taxon

The analysis of environmental microbial communities has largely relied on a PCR-dependent amplification of genes entailing species identity as 16S rRNA. This approach is susceptible to biases depending on the level of primer matching in different species. Moreover, possible yet-to-discover taxa whose rRNA could differ enough from known ones would not be revealed. DNA-based methods moreover do not provide information on the actual physiological relevance of each taxon within an environment and are affected by the variable number of rRNA operons in different genomes. To overcome these drawbacks we propose an approach of direct sequencing of 16S ribosomal RNA without any primer- or PCR-dependent step. The method was tested on a microbial community developing in an anammox bioreactor sampled at different time-points. A conventional PCR-based amplicon pyrosequencing was run in parallel. The community resulting from direct rRNA sequencing was highly consistent with the known biochemical processes operative in the reactor. As direct rRNA-seq is based not only on taxon abundance but also on physiological activity, no comparison between its results and those from PCR-based approaches can be applied. The novel principle is in this respect proposed not as an alternative but rather as a complementary methodology in microbial community studies

Nonischemic left ventricular scar as a substrate of life-threatening ventricular arrhythmias and sudden cardiac death in competitive athletes

Background\u2014The clinical profile and arrhythmic outcome of competitive athletes with isolated nonischemic left ventricular (LV) scar as evidenced by contrast-enhanced cardiac magnetic resonance remain to be elucidated. Methods and Results\u2014We compared 35 athletes (80% men, age: 14\u201348 years) with ventricular arrhythmias and isolated LV subepicardial/midmyocardial late gadolinium enhancement (LGE) on contrast-enhanced cardiac magnetic resonance (group A) with 38 athletes with ventricular arrhythmias and no LGE (group B) and 40 healthy control athletes (group C). A stria LGE pattern with subepicardial/midmyocardial distribution, mostly involving the lateral LV wall, was found in 27 (77%) of group A versus 0 controls (group C; P<0.001), whereas a spotty pattern of LGE localized at the junction of the right ventricle to the septum was respectively observed in 11 (31%) versus 10 (25%; P=0.52). All athletes with stria pattern showed ventricular arrhythmias with a predominant right bundle branch block morphology, 13 of 27 (48%) showed ECG repolarization abnormalities, and 5 of 27 (19%) showed echocardiographic hypokinesis of the lateral LV wall. The majority of athletes with no or spotty LGE pattern had ventricular arrhythmias with a predominant left bundle branch block morphology and no ECG or echocardiographic abnormalities. During a follow-up of 38\ub125 months, 6 of 27 (22%) athletes with stria pattern experienced malignant arrhythmic events such as appropriate implantable cardiac defibrillator shock (n=4), sustained ventricular tachycardia (n=1), or sudden death (n=1), compared with none of athletes with no or LGE spotty pattern and controls. Conclusions\u2014Isolated nonischemic LV LGE with a stria pattern may be associated with life-threatening arrhythmias and sudden death in the athlete. Because of its subepicardial/midmyocardial location, LV scar is often not detected by echocardiography

Crescere: Studio longitudinale per il benessere dell´infanzia

La transizione dall’infanzia all’adolescenza è un momento chiave nella vita di una persona. Si affrontano numerose sfide e compiti di sviluppo, che aiutano la persona a potenziare le capacità e a formare la propria identità. Quali fattori favoriscono la crescita positiva e proteggono dai rischi? È la domanda principale dello studio CRESCERE. I risultati mettono in luce i circoli virtuosi che si possono sviluppare nella vita dei ragazzi. Emerge l’importanza dei legami familiari, del dialogo con i genitori, del supporto che percepiscono dalla famiglia e di quanto sia importante per promuovere la fiducia nelle proprie capacità, il sentirsi bene con se stessi e con gli altri. Il benessere scolastico è un altro aspetto fondamentale per la crescita, per lo sviluppo psicologico e sociale dei ragazzi.Fil: Barbero Vignola, G. Fondazione Emanuela Zancan; ItaliaFil: Bezze, Maria. Fondazione Emanuela Zancan; ItaliaFil: Canali, Cinzia. Fondazione Emanuela Zancan; ItaliaFil: Crocetti, Elisabetta. Università di Bologna; ItaliaFil: De Leo, Diego. Griffith University; AustraliaFil: Eynard, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones y Estudios sobre Cultura y Sociedad. Universidad Nacional de Córdoba. Centro de Investigaciones y Estudios sobre Cultura y Sociedad; ArgentinaFil: Maurizio, Roberto. Fondazione Emanuela Zancan; ItaliaFil: Milan, Giuseppe. Università di Padova; ItaliaFil: Ongaro, Fausta. Università di Padova; ItaliaFil: Schiavon, Maurizio. Centro di Medicina dello Sport ; ItaliaFil: Vecchiato, Tiziano. Fondazione Emanuela Zancan; Itali