Using globular clusters to test gravity in the weak acceleration regime: NGC 7099

A test of Newton's law of gravity in the low acceleration regime using globular clusters is presented. New results for the core collapsed globular cluster NGC 7099 are given. The run of the gravitational potential as a function of distance is probed studying the velocity dispersion profile of the cluster, as derived from a set of 125 radial velocities with accuracy better than 1 km/s. The velocity dispersion profile is traced up to ~18 pc from the cluster center. The dispersion is found to be maximal at the center, then decrease until 10+-2 pc from the center, well inside the cluster tidal radius of 42 pc. After that the dispersion remains constant with average value 2.2+-0.3 km/s. Assuming for NGC 7099 a total V mag of M(V)=-7.43 mags and mass-to-light ratio M/L=1, the acceleration at 10 pc from the center is 1.1e-8 cm/s/s. Thus, the flattening of the velocity dispersion profile occurs for a value of the internal acceleration of gravity fully consistent with a_0=1.2e-8 cm/s/s observed in galaxies. This new result for NGC 7099 brings to 4 the clusters with velocity dispersion profile probing acceleration below a_0. All four have been found to have a flat dispersion profile at large radii where the acceleration is below a_0, mimicking qualitatively and quantitatively elliptical galaxies. Whether this indicates a failure of Newtonian dynamics in the low acceleration limit or some more conventional dynamical effect (e.g., tidal heating) is still unclear. However, the similarities emerging between very different globular clusters, as well as between globular clusters and elliptical galaxies seem to favor the first of these two possibilities.Comment: Accepted for publication in A&A Letters. Four pages in tota

Using globular clusters to test gravity in the weak acceleration regime

We report on the results from an ongoing program aimed at testing Newton's law of gravity in the low acceleration regime using globular clusters. It is shown that all clusters studied so far do behave like galaxies, that is, their velocity dispersion profile flattens out at large radii where the acceleration of gravity goes below 1e-8 cm/s/s, instead of following the expected Keplerian fall off. In galaxies this behavior is ascribed to the existence of a dark matter halo. Globular clusters, however, do not contain dark matter, hence this result might indicate that our present understanding of gravity in the weak regime of accelerations is incomplete and somehow incorrect.Comment: As published on the European Southern Observatory "the Messenger", Num. 128, June 2007. Seven pages, 4 figures, 2 table

The inelastic hard dimer gas: a non-spherical model for granular matter

We study a two-dimensional gas of inelastic smooth hard dimers. Since the collisions between dimers are dissipative, being characterized by a coefficient of restitution $\alpha<1$, and no external driving force is present, the energy of the system decreases in time and no stationary state is achieved. However, the resulting non equilibrium state of the system displays several interesting properties in close analogy with systems of inelastic hard spheres, whose relaxational dynamics has been thoroughly explored. We generalise to inelastic systems a recently method introduced [G.Ciccotti and G.Kalibaeva, J. Stat. Phys. {\bf 115}, 701 (2004)] to study the dynamics of rigid elastic bodies made up of different spheres hold together by rigid bonds. Each dimer consists of two hard disks of diameter $d$, whose centers are separated by a fixed distance $a$. By describing the rigid bonds by means of holonomic constraints and deriving the appropriate collision rules between dimers, we reduce the dynamics to a set of equations which can be solved by means of event driven simulation. After deriving the algorithm we study the decay of the total kinetic energy, and of the ratio between the rotational and the translational kinetic energy of inelastic dimers. We show numerically that the celebrated Haff's homogeneous cooling law $t^{-2}$, describing how the kinetic energy of an inelastic hard sphere system with constant coefficient of restitution decreases in time, holds even in the case of these non spherical particles. We fully characterize this homogeneous decay process in terms of appropriate decay constants and confirm numerically the scaling behavior of the velocity distributions.Comment: 21 pages, 6 figures and 2 tables, submitted to JC

Multi-phase outflows in Mkn 848 observed with SDSS-MaNGA Integral Field Spectroscopy

The characterisation of galaxy-scale outflows in terms of their multi-phase nature, amount, and effects of flowing material is crucial to place constraints on models of galaxy evolution. This study can proceed only with the detailed investigation of individual targets. We present a spatially resolved spectroscopic optical data analysis of Mkn 848, a complex system consisting of two merging galaxies at z~0.04 that are separated 7.5 kpc (projected distance). Motivated by the presence of a multi-phase outflow in the north-west system revealed by the SDSS integrated spectrum, we analysed the publicly available MaNGA data, which cover almost the entire merging system, to study the physical properties of cool and warm gas in detail. Galaxy-wide outflowing gas in multiple phases is revealed for the first time in the two merging galaxies. We also detect spatially resolved resonant NaID emission associated with the outflows. The derived outflow energetics may be consistent with a scenario in which both winds are accelerated by stellar processes and AGN activity, although we favour an AGN origin given the high outflow velocities and the ionisation conditions observed in the outflow regions. Deeper observations are required, however, to better constrain the nature of these multi-phase outflows. Outflow energetics in the north-west system are strongly different between the ionised and atomic gas components, the latter of which is associated with mass outflow rate and kinetic and momentum powers that are 1-2 dex higher; those associated with the south-east galaxy are instead similar. Strong kp-scale outflows are revealed in an ongoing merger system, suggesting that feedback can potentially impact the host galaxy even in the early merger phases. The characterisation of the neutral and ionised gas phases has proved to be crucial for a comprehensive study of the outflow phenomena.Comment: 19 pages, 14 figures, accepted for publication in A&

Formal verification of storm topologies through D-VerT

Data-intensive applications (DIAs) based on so-called Big Data technologies are nowadays a common solution adopted by IT companies to face their growing computational needs. The need for highly reliable applications able to handle huge amounts of data and the availability of infrastructures for distributed computing rapidly led industries to develop frame-works for streaming and big-data processing, like Apache Storm and Spark. The definition of methodologies and principles for good software design is, therefore, fundamental to support the development of DIAs. This paper presents an approach for non-functional analysis of DIAs through D- VerT, a tool for the architectural assessment of Storm applications. The verification is based on a translation of Storm topologies into the CLTLoc metric temporal logic. It allows the designer of a Storm application to check for the existence of components that cannot process their workload in a timely manner, typically due to an incorrect design of the topology

Abundance analysis of a sample of evolved stars in the outskirts of Omega Centauri

The globular cluster $\omega$ Centauri (NGC 5139) is a puzzling stellar system harboring several distinct stellar populations whose origin still represents a unique astrophysical challenge. Current scenarios range from primordial chemical inhomogeneities in the mother cloud to merging of different sub-units and/or subsequent generations of enriched stars - with a variety of different pollution sources- within the same potential well. In this paper we study the chemical abundance pattern in the outskirts of Omega Centauri, half-way to the tidal radius (covering the range of 20-30 arcmin from the cluster center), and compare it with chemical trends in the inner cluster regions, in an attempt to explore whether the same population mix and chemical compositions trends routinely found in the more central regions is also present in the cluster periphery.We extract abundances of many elements from FLAMES/UVES spectra of 48 RGB stars using the equivalent width method and then analyze the metallicity distribution function and abundance ratios of the observed stars. We find, within the uncertainties of small number statistics and slightly different evolutionary phases, that the population mix in the outer regions cannot be distinguished from the more central regions, although it is clear that more data are necessary to obtain a firmer description of the situation. From the abundance analysis, we did not find obvious radial gradients in any of the measured elements.Comment: 22 pages, 8 eps figures, in press in New Astronom

Theoretical fits of the \delta Cephei light, radius and radial velocity curves

We present a theoretical investigation of the light, radius and radial velocity variations of the prototype $\delta$ Cephei. We find that the best fit model accounts for luminosity and velocity amplitudes with an accuracy better than $0.8\sigma$, and for the radius amplitude with an accuracy of $1.7\sigma$. The chemical composition of this model suggests a decrease in both helium (0.26 vs 0.28) and metal (0.01 vs 0.02) content in the solar neighborhood. Moreover, distance determinations based on the fit of light curves agree at the $0.8\sigma$ level with the trigonometric parallax measured by the Hubble Space Telescope (HST). On the other hand, distance determinations based on angular diameter variations, that are independent of interstellar extinction and of the $p$-factor value, indicate an increase of the order of 5% in the HST parallax.Comment: accepted for publication on ApJ Letter

Clostridioides difficile Infection in Patients with Inflammatory Bowel Disease May be Favoured by the Effects of Proinflammatory Cytokines on the Enteroglial Network

Clostridioides difficile infection is widespread throughout countries and represents an important cause of nosocomial diarrhoea, with relatively high morbidity. This infection often occurs in patients with inflammatory bowel diseases and may complicate their clinical picture. Here, we propose, on the basis of evidence from basic science studies, that in patients affected by inflammatory bowel diseases, this infection might be facilitated by a derangement of the enteric glial cell (EGC) network caused by the effects of proinflammatory cytokines, such as tumour necrosis factor alpha and interferon gamma, which enhance the cytotoxic effects of C. difficile toxin B on EGCs. This hypothesis, if confirmed, could open the door to alternative treatment approaches to fight C. difficile infection

The Addition of Venetoclax to Induction Chemotherapy in No Low-Risk AML Patients: A Propensity Score-Matched Analysis of the Gimema AML1718 and AML1310 Trials

Venetoclax combined with intensive chemotherapy proved to be safe with promising activity in fit patients with no-low-risk newly diagnosed acute myeloid leukemia (AML), as demonstrated also by an intermediate analysis of the GIMEMA AML1718 trial (NCT03455504). The latter trial, still ongoing, is based on the administration of venetoclax-FLAI to intermediate/high-risk ELN2017 AML and produced a complete remission (CR) rate of 84%, a minimal residual disease (MRD)-negativity rate of 74% and a 12-month Overall Survival (OS) and disease-free survival (DFS) of 75.7% (95%CI: 64.1%, 89.5%) and 80.7% (95%CI: 67.9%, 95.9%), respectively. In order to evaluate the actual advantage of the addition of venetoclax to chemotherapy, the GIMEMA AML1718 was matched to AML1310, which entailed a "3+7"-like induction and a risk-adapted, MRD-directed post-remission transplant allocation (NCT01452646, Venditti et al - Blood 2019). To generate a reliable comparison, AML1718 and AML1310 were matched by using a propensity score and then compared in terms of CR achievement, MRD-negativity and survival outcomes. Patient-level data from GIMEMA AML1718 (n=57) and AML1310 (N=445) with ELN2017 risk classification available were used to conduct a propensity score matching analysis, widely used for reducing the effects of confounding when estimating the effects of treatment on outcomes. Conditional on the propensity score, the distribution of measured variables is expected to be the same in treated (i.e. AML1718) and control (i.e. AML1310) subjects. In the present propensity score model, we included the following variables: age at diagnosis, gender, ELN2017 risk classification and transplant. Different methods for matching were attempted, including 1:1 nearest neighbor, full-matching, optimal matching (1:2, 1:3 and 1:4) and 1:2 genetic matching. The methods employed for assessing balancing were: i) Standardized Mean Difference - Love plot, ii) Empirical cumulative density function, iii) Variance ratio, iv) Empirical QQ-plot. Weights were calculated with probit or logit regression models according to the propensity score method used. Weights obtained from full-matching were used to adjust outcomes (CR, MRD negativity and survival outcomes). No patients were dropped in the full-matching process. A standardized bias score less than 0.25 was used as a criterion for adequate balancing. We used balance tables and Love plots to assess for covariate balance before and after matching. Survival curves were compared by Log-rank test and Restricted Mean Survival Time (RMST) at 12 months. AML1718 and AML1310 cohorts differed in terms of age (median: 54 vs 49 years, p=0.003) and risk category (p&lt; .0001) - since the low risk was not represented in AML1718 trial - and female sex (35% vs 48%, p=0.069), though to a lesser extent. Contrariwise, the percentage of transplanted patients was comparable before matching (49% vs 49%, p=0.96). Being more recent, AML1718 median follow-up was shorter than AML1310 (10.5 vs 75.8 months). Full-matching, 1:2 optimal matching and 1:2 genetic matching produced the best balancing. Table 1 shows the results of the analysis for the unmatched and matched data. After balancing, according to all matching methods, the CR rate observed in the AML1718 was significantly higher than AML1310, as well as MRD-negativity rate. Comparing survival outcomes at 12 months, emerged that, upon matching, OS and DFS estimates of the AML1718 were higher than those of AML1310, though a slight statistical significance was reached only with the optimal matching on DFS (p=0.042). This result was confirmed by a statistically significant difference between the two RMST at 12 months (p=0.036). Despite this, a longer AML1718 follow-up is needed to provide a robust comparison between the two protocols. Our propensity-score analysis showed that combining venetoclax with chemotherapy in newly diagnosed AML patients resulted in improved outcomes in terms of CR rate and MRD-negativity: these achievements are crucial to allow transition to allogenic transplantation in first remission. With regards to survival outcomes, a solid conclusion will be drawn when a longer AML1718 follow-up is available. These preliminary results highlight the incremental benefit of venetoclax added to intensive induction chemotherapy and paves the way to novel combination regimens based on venetoclax

Silent Cerebral Ischemia Detected With Diffusion-Weighted Imaging in Patients Treated With Protected and Unprotected Carotid Artery Stenting

Background and Purpose— Percutaneous transluminal angioplasty with stent (CAS) is an alternative method to endarterectomy in the revascularization of carotid artery stenosis. Protected CAS is currently used to prevent distal embolization. Diffusion-weighted MRI (DWI) is the most sensitive tool to evaluate silent cerebral ischemia. The purpose of this research was to assess the incidence of cerebral embolic lesions during CAS and to evaluate whether cerebral protection devices can reduce the number of silent cerebral ischemia with respect to unprotected CAS. Methods— Fifty-two patients with high-grade internal stenosis underwent CAS; 30 patients (group a) were treated with a cerebral protection device, and 22 (group b) were treated without it. All of the patients were evaluated preoperatively and postoperatively with fluid-attenuated inversion recovery and DWI sequences to depict the number of new embolic silent cerebral lesions. Results— Embolic silent cerebral lesions occurred in 30% of CAS. Cerebral protection devices reduce the number of new lesions significantly reducing the consistent lesions ipsilateral to the treated vessel. Inconsistent lesions do not differ in both groups of patients. Clinical, radiological, and procedural variables do not correlate with the appearance of new cerebral lesions. Conclusions— Embolic cerebral lesions detected with DWI are more frequent with unprotected CAS, although they are present also with the use of cerebral protection devices. Probably a part of silent cerebral lesions arise from the procedural maneuver in the aortic arch