A population of binaries in the Asymptotic Giant Branch of 47 Tucanae?

We have used a set of archived Hubble Space Telescope/ACS images to probe the evolved populations of the globular cluster 47 Tucanae. We find an excess of Asymptotic Giant Branch (AGB) stars in the cluster core. We interpret this feature as the signature of an extra-population likely made by the progeny of massive stars originated by the evolution of binary systems. Indeed the comparison with theoretical tracks suggests that the AGB population of 47 Tuc can be significantly contaminated by more massive stars currently experiencing the first ascending Red Giant Branch.Comment: 14 pages, 4 figures, in press on ApJ Letter

A complete census of HαH\alpha emitters in NGC 6397

We used a dataset of archival Hubble Space Telescope images obtained through the F555W, F814W and F656N filters, to perform a complete search for objects showing $H\alpha$ emission in the globular cluster NGC 6397. As photometric diagnostic, we used the $(V-H\alpha)_0$ color excess in the $(V-H\alpha)_0$-$(V-I)_0$ color-color diagram. In the analysed field of view, we identified 53 $H\alpha$ emitters. In particular, we confirmed the optical counterpart to 20 X-ray sources (7 cataclysmic variables, 2 millisecond pulsars and 11 active binaries) and identified 33 previously unknown sources, thus significantly enlarging the population of known active binaries in this cluster. We report the main characteristics for each class of objects. Photometric estimates of the equivalent width of the $H\alpha$ emission line, were derived from the $(V-H\alpha)_0$-excess and, for the first time, compared to the spectroscopic measurements obtained from the analysis of MUSE spectra. The very good agreement between the spectroscopic and photometric measures fully confirmed the reliability of the proposed approach to measure the $H\alpha$ emission. The search demonstrated the efficiency of this novel approach to pinpoint and measure $H\alpha$-emitters, thus offering a powerful tool to conduct complete census of objects whose formation and evolution can be strongly affected by dynamical interactions in star clusters.Comment: Accepted for publication by ApJ; 14 pages, 8 Figures, 1 Tabl

Modelling the Observed Stellar Mass Function and its Radial Variation in Galactic Globular Clusters

We measure how the slope $\alpha$ of the stellar mass function (MF) changes as a function of clustercentric distance $r$ in five Galactic globular clusters and compare $\alpha(r)$ to predictions from direct $N$-body star cluster simulations. Theoretical studies predict that $\alpha(r)$ (which traces the degree of mass segregation in a cluster) should steepen with time as a cluster undergoes two-body relaxation and that the amount by which the global MF can evolve from its initial state due to stellar escape is directly linked to $\alpha(r)$. We find that the amount of mass segregation in M10, NGC 6218, and NGC 6981 is consistent with their dynamical ages, but only the global MF of M10 is consistent with its degree of mass segregation as well. NGC 5466 and NGC 6101 on the other hand appear to be less segregated than their dynamical ages would indicate. Furthermore, despite the fact that the escape rate of stars in non-segregated clusters is independent of stellar mass, both NGC 5466 and NGC 6101 have near-flat MFs. We discuss various mechanisms which could produce non-segregated clusters with near-flat MFs, including higher mass-loss rates and black hole retention, but argue that for some clusters (NGC 5466 and NGC 6101) explaining the present-day properties might require either a non-universal IMF or a much more complex dynamical history.Comment: 12 pages, 9 figures, Accepted for publication in MNRA

The central Blue Straggler population in four outer-halo globular clusters

Using HST/WFPC2 data, we have performed a comparative study of the Blue Straggler Star (BSS) populations in the central regions of the globular clusters AM 1, Eridanus, Palomar 3, and Palomar 4. Located at distances RGC > 50 kpc from the Galactic Centre, these are (together with Palomar 14 and NGC 2419) the most distant clusters in the Halo. We determine their colour-magnitude diagrams and centres of gravity. The four clusters turn out to have similar ages (10.5-11 Gyr), significantly smaller than those of the inner-Halo globulars, and similar metallicities. By exploiting wide field ground based data, we build the most extended radial density profiles from resolved star counts ever published for these systems. These are well reproduced by isotropic King models of relatively low concentration. BSSs appear to be significantly more centrally segregated than red giants in all globular clusters, in agreement with the estimated core and half-mass relaxation times which are smaller than the cluster ages. Assuming that this is a signature of mass segregation, we conclude that AM 1 and Eridanus are slightly dynamically more evolved than Pal 3 and Pal 4.Comment: Accepted for publication in ApJ, references update

Discovery of a double Blue Straggler sequence in M15: new insight into the core-collapse process

In this paper we report on the discovery of a double blue straggler star (BSS) sequence in the core of the core-collapsed cluster M15 (NGC 7078). We performed a detailed photometric analysis of the extremely dense core of the cluster using a set of images secured with the Advanced Camera for Survey in the High Resolution Channel mode on-board the Hubble Space Telescope. The proper combination of the large number of single frames in the near-UV (F220W), and blue (F435W) filters allowed us to perform a superb modeling of the Point Spread Function and an accurate deblending procedure. The Color-Magnitude diagram revealed the presence of two distinct parallel sequences of blue stragglers. In particular, the blue BSS sequence is characterized by the intriguing presence of two different branches. The first branch appears extremely narrow, it extends up to 2.5 magnitudes brighter than the cluster main-sequence turnoff (MS-TO) point, and it is nicely reproduced by a 2 Gyr-old collisional isochrone. The second branch extends up to 1.5 magnitudes from the MS-TO and it is reproduced by a 5.5 Gyr-old collisional isochrone. Our observations suggest that each of these branches is mainly constituted by a population of nearly coeval collisional BSS of different masses generated during two episodes of high collisional activity. We discuss the possibility that the oldest episode corresponds to the core-collapse event (occurred about 5.5 Gyr ago), while the most recent one (occurred about 2 Gyr ago) is associated with a core oscillation in the post-core collapse evolution. The discovery of these features provides further strong evidence in support of the connection between the BSS properties and GC dynamical evolution, and it opens new perspectives on the study of core-collapse and post core-collapse evolution.Comment: Accepted for publication on Ap

Three new bricks in the wall: Berkeley 23, Berkeley 31, and King 8

A comprehensive census of Galactic open cluster properties places unique constraints on the Galactic disc structure and evolution. In this framework we investigate the evolutionary status of three poorly-studied open clusters, Berkeley 31, Berkeley 23 and King 8, all located in the Galactic anti-centre direction. To this aim, we make use of deep LBT observations, reaching more than 6 mag below the main sequence Turn- Off. To determine the cluster parameters, namely age, metallicity, distance, reddening and binary fraction, we compare the observational colour-magnitude diagrams (CMDs) with a library of synthetic CMDs generated with different evolutionary sets (Padova, FRANEC and FST) and metallicities. We find that Berkeley 31 is relatively old, with an age between 2.3 and 2.9 Gyr, and rather high above the Galactic plane, at about 700 pc. Berkeley 23 and King 8 are younger, with best fitting ages in the range 1.1-1.3 Gyr and 0.8-1.3 Gyr, respectively. The position above the Galactic plane is about 500- 600 pc for the former, and 200 pc for the latter. Although a spectroscopic confirmation is needed, our analysis suggests a sub-solar metallicity for all three clusters.Comment: 17 Pages, Accepted for publication in MNRA

Term amniotic membrane is a high throughput source for multipotent mesenchymal stem cells with the ability to differentiate into endothelial cells in vitro

BACKGROUND: Term Amniotic membrane (AM) is a very attractive source of Mesenchymal Stem Cells (MSCs) due to the fact that this fetal tissue is usually discarded without ethical conflicts, leading to high efficiency in MSC recovery with no intrusive procedures. Here we confirmed that term AM, as previously reported in the literature, is an abundant source of hMSCs; in particular we further investigated the AM differentiation potential by assessing whether these cells may also be committed to the angiogenic fate. In agreement with the recommendation of the International Society for Cellular Therapy, the mesenchymal cells herein investigated were named Amniotic Membrane-human Mesenchymal Stromal Cells (AM-hMSC). RESULTS: The recovery of hMSCs and their in vitro expansion potential were greater in amniotic membrane than in bone marrow stroma. At flow cytometry analysis AM-hMSCs showed an immunophenotypical profile, i.e., positive for CD105, CD73, CD29, CD44, CD166 and negative for CD14, CD34, CD45, consistent with that reported for bone marrow-derived MSCs. In addition, amniotic membrane-isolated cells underwent in vitro osteogenic (von Kossa stain), adipogenic (Oil Red-O stain), chondrogenic (collagen type II immunohistochemichal detection) and myogenic (RT-PCR MyoD and Myogenin expression as well as desmin immunohistochemical detection) differentiation. In angiogenic experiments, a spontaneous differentiation into endothelial cells was detected by in vitro matrigel assay and this behaviour has been enhanced through Vascular Endothelial Growth Factor (VEGF) induction. According to these findings, VEGF receptor 1 and 2 (FLT-1 and KDR) were basally expressed in AM-hMSCs and the expression of endothelial-specific markers like FLT-1 KDR, ICAM-1 increased after exposure to VEGF together with the occurrence of CD34 and von Willebrand Factor positive cells. CONCLUSION: The current study suggests that AM-hMSCs may emerge as a remarkable tool for the cell therapy of multiple diseased tissues. AM-hMSCs may potentially assist both bone and cartilage repair, nevertheless, due to their angiogenic potential, they may also pave the way for novel approaches in the development of tissue-engineered vascular grafts which are useful when vascularization of ischemic tissues is required

Single-cell resolution analysis of the human pancreatic ductal progenitor cell niche.

We have described multipotent progenitor-like cells within the major pancreatic ducts (MPDs) of the human pancreas. They express PDX1, its surrogate surface marker P2RY1, and the bone morphogenetic protein (BMP) receptor 1A (BMPR1A)/activin-like kinase 3 (ALK3), but not carbonic anhydrase II (CAII). Here we report the single-cell RNA sequencing (scRNA-seq) of ALK3bright+-sorted ductal cells, a fraction that harbors BMP-responsive progenitor-like cells. Our analysis unveiled the existence of multiple subpopulations along two major axes, one that encompasses a gradient of ductal cell differentiation stages, and another featuring cells with transitional phenotypes toward acinar tissue. A third potential ducto-endocrine axis is revealed upon integration of the ALK3bright+ dataset with a single-cell whole-pancreas transcriptome. When transplanted into immunodeficient mice, P2RY1+/ALK3bright+ populations (enriched in PDX1+/ALK3+/CAII− cells) differentiate into all pancreatic lineages, including functional β-cells. This process is accelerated when hosts are treated systemically with an ALK3 agonist. We found PDX1+/ALK3+/CAII− progenitor-like cells in the MPDs of types 1 and 2 diabetes donors, regardless of the duration of the disease. Our findings open the door to the pharmacological activation of progenitor cells in situ.post-print3.184 K

Early impairment in left ventricular longitudinal systolic function is associated with an increased risk of incident atrial fibrillation in patients with type 2 diabetes

It is known that type 2 diabetic patients are at high risk of atrial fibrillation (AF). However, the early echocardiographic determinants of AF vulnerability in this patient population remain poorly known

Gastrointestinal presentation of kawasaki disease: A red flag for severe disease?

Background Kawasaki disease (KD) is a febrile systemic vasculitis of unknown etiology and the main cause of acquired heart disease among children in the developed world. To date, abdominal involvement at presentation is not recognized as a risk factor for a more severe form of the disease. Objective To evaluate whether presenting abdominal manifestations identify a group at major risk for Intravenous immunoglobulin (IVIG)-resistance and coronary lesions. Methods Retrospective study of KD patients diagnosed between 2000 and 2015 in 13 pediatric units in Italy. Patients were divided into 2 groups according to the presence or absence of abdominal manifestations at onset. We compared their demographic and clinical data, IVIG-responsiveness, coronary ectasia/aneurysms, laboratory findings from the acute and subacute phases. Results 302 patients (181 boys) were enrolled: 106 patients with, and 196 patients without presenting abdominal features. Seasonality was different between the groups (p = 0.034). Patients with abdominal manifestations were younger (p = 0.006) and more frequently underwent delayed treatment (p = 0.014). In the acute phase, patients with abdominal presentation had higher platelet counts (PLT) (p = 0.042) and lower albuminemia (p = 0.009), while, in the subacute phase, they had higher white blood cell counts (WBC) and PLT (p = 0.002 and p < 0.005, respectively) and lower red blood cell counts (RBC) and hemoglobin (Hb) (p = 0.031 and p 0.009). Moreover, the above mentioned group was more likely to be IVIG-resistant (p < 0.005) and have coronary aneurysms (p = 0.007). In the multivariate analysis, presenting abdominal manifestations, age younger than 6 months, IVIG- resistance, delayed treatment and albumin concentration in the acute phase were independent risk factors for coronary aneurysms (respectively p<0.005, <0.005, = 0.005 and 0.009). Conclusions This is the first multicenter report demonstrating that presenting gastrointestinal features in KD identify patients at higher risk for IVIG-resistance and for the development of coronary aneurysms in a predominantly Caucasian population