A dynamical mechanism for the origin of nuclear rings

We develop a dynamical theory for the origin of nuclear rings in barred galaxies. In analogy with the standard theory of accretion discs, our theory is based on shear viscous forces among nested annuli of gas. However, the fact that gas follows non circular orbits in an external barred potential has profound consequences: it creates a region of reverse shear in which it is energetically favourable to form a stable ring which does not spread despite dissipation. Our theory allows us to approximately predict the size of the ring given the underlying gravitational potential. The size of the ring is loosely related to the location of the Inner Lindblad Resonance in the epicyclic approximation, but the predicted location is more accurate and is also valid for strongly barred potentials. By comparing analytical predictions with the results of hydrodynamical simulations, we find that our theory provides a viable mechanism for ring formation if the effective sound speed of the gas is low (\cs\lesssim1\kms), but that nuclear spirals/shocks created by pressure destroy the ring when the sound speed is high (\cs\simeq10\kms). We conclude that whether this mechanism for ring formation is relevant for real galaxies ultimately depends on the effective equation of state of the ISM. Promising confirmation comes from simulations in which the ISM is modelled using state-of-the-art cooling functions coupled to live chemical networks, but more tests are needed regarding the role of turbulence driven by stellar feedback. If the mechanism is relevant in real galaxies, it could provide a powerful tool to constrain the gravitational potential, in particular the bar pattern speed.Comment: Accepted for publication in MNRA

Acquisition and preliminary analysis of multi-channel seismic reflection data, acquired during the oceanographic cruises of the TOMO-ETNA experiment

The TOMO-ETNA experiment was performed in the framework of the FP7 “MED-SUV” (MEDiterranean SUpersite Volcanoes) in order to gain a detailed geological and structural model of the continental and oceanic crust concerning Etna and Aeolian Islands volcanoes (Sicily, Italy), by means of active and passive seismic exploration methodologies. Among all data collected, some 1410 km of marine multi-channel seismic (MCS) reflection profiles were acquired in the Ionian and Tyrrhenian Seas during two of the three oceanographic cruises of the TOMO-ETNA experiment, in July and November 2014, with the aim of shading light to deep, intermediate and shallow stratigraphy and crustal structure of the two above mentioned areas. The MCS sections, targeted to deep exploration, were acquired during the oceanographic cruise on board of the R/V “Sarmiento de Gamboa”, using an active seismic source of 16 air-guns, for a total volume of 4340 cu. in., and a 3000 m long, 240-channels digital streamer as receiving system. High-resolution seismic profiles were instead collected through the R/V “Aegaeo”, using two smaller air-guns (overall 270 cu. in. volume) and a 96 channels, 300 m long digital streamer. This paper provides a detailed description of the acquisition parameters and main processing steps adopted for the MCS data. Some processed lines are shown and preliminarily interpreted, to highlight the overall good quality and the high potential of the MCS sections collected during the TOMO-ETNA experiment. © 2016 by the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved

Defining responders to therapies by a statistical modeling approach applied to randomized clinical trial data

Background: Personalized medicine is the tailoring of treatment to the individual characteristics of patients. Once a treatment has been tested in a clinical trial and its effect overall quantified, it would be of great value to be able to use the baseline patients' characteristics to identify patients with larger/lower benefits from treatment, for a more personalized approach to therapy. Methods: We show here a previously published statistical method, aimed at identifying patients' profiles associated to larger treatment benefits applied to three identical randomized clinical trials in multiple sclerosis, testing laquinimod vs placebo (ALLEGRO, BRAVO, and CONCERTO). We identified on the ALLEGRO patients' specific linear combinations of baseline variables, predicting heterogeneous response to treatment on disability progression. We choose the best score on the BRAVO, based on its ability to identify responders to treatment in this dataset. We finally got an external validation on the CONCERTO, testing on this new dataset the performance of the score in defining responders and non-responders. Results: The best response score defined on the ALLEGRO and the BRAVO was a linear combination of age, sex, previous relapses, brain volume, and MRI lesion activity. Splitting patients into responders and non-responders according to the score distribution, in the ALLEGRO, the hazard ratio (HR) for disability progression of laquinimod vs placebo was 0.38 for responders, HR = 1.31 for non-responders (interaction p = 0.0007). In the BRAVO, we had similar results: HR = 0.40 for responders and HR = 1.24 for non-responders (interaction p = 0.006). These findings were successfully replicated in the CONCERTO study, with HR = 0.44 for responders and HR=1.08 for non-responders (interaction p = 0.033). Conclusions: This study demonstrates the possibility to refine and personalize the treatment effect estimated in randomized studies by using the baseline demographic and clinical characteristics of the included patients. The method can be applied to any randomized trial in any medical condition to create a treatment-specific score associated to different levels of response to the treatment tested in the trial. This is an easy and affordable method toward therapy personalization, indicating patient profiles related to a larger benefit from a specific drug, which may have implications for taking clinical decisions in everyday clinical practice

Jeans modelling of the Milky Way's nuclear stellar disc

The nuclear stellar disc (NSD) is a flattened stellar structure that dominates the gravitational potential of the Milky Way at Galactocentric radii 30≲R≲300pc⁠. In this paper, we construct axisymmetric Jeans dynamical models of the NSD based on previous photometric studies and we fit them to line-of-sight kinematic data of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and silicon monoxide (SiO) maser stars. We find that (i) the NSD mass is lower but consistent with the mass independently determined from photometry by Launhardt et al. Our fiducial model has a mass contained within spherical radius r=100pc of M(r 1. Observations and theoretical models of the star-forming molecular gas in the central molecular zone suggest that large vertical oscillations may be already imprinted at stellar birth. However, the finding σz/σR > 1 depends on a drop in the velocity dispersion in the innermost few tens of parsecs, on our assumption that the NSD is axisymmetric, and that the available (extinction corrected) stellar samples broadly trace the underlying light and mass distributions, all of which need to be established by future observations and/or modelling. (iii) We provide the most accurate rotation curve to date for the innermost 500pc of our Galaxy

Orbital analysis of stars in the nuclear stellar disc of the Milky Way

Context. While orbital analysis studies were so far mainly focused on the Galactic halo, it is possible now to do these studies in the heavily obscured region close to the Galactic Centre.Aims. We aim to do a detailed orbital analysis of stars located in the nuclear stellar disc (NSD) of the Milky Way allowing us to trace the dynamical history of this structure.Methods. We integrated orbits of the observed stars in a non-axisymmetric potential. We used a Fourier transform to estimate the orbital frequencies. We compared two orbital classifications, one made by eye and the other with an algorithm, in order to identify the main orbital families. We also compared the Lyapunov and the frequency drift techniques to estimate the chaoticity of the orbits.Results. We identified several orbital families as chaotic, z-tube, x-tube, banana, fish, saucer, pretzel, 5:4, and 5:6 orbits. As expected for stars located in a NSD, the large majority of orbits are identified as z-tubes (or as a sub-family of z-tubes). Since the latter are parented by x2 orbits, this result supports the contribution of the bar (in which x2 orbits are dominant in the inner region) in the formation of the NSD. Moreover, most of the chaotic orbits are found to be contaminants from the bar or bulge which would confirm the predicted contamination from the most recent NSD models.Conclusions. Based on a detailed orbital analysis, we were able to classify orbits into various families, most of which are parented by x2-type orbits, which are dominant in the inner part of the bar

The cytosolic glutamine synthetase GLN1;2 plays a role in the control of plant growth and ammonium homeostasis in Arabidopsis rosettes when nitrate supply is not limiting

Glutamine synthetase (EC 6.3.1.2) is a key enzyme of ammonium assimilation and recycling in plants where it catalyses the synthesis of glutamine from ammonium and glutamate. In Arabidopsis, five GLN1 genes encode GS1 isoforms. GLN1;2 is the most highly expressed in leaves and is over-expressed in roots by ammonium supply and in rosettes by ample nitrate supply compared with limiting nitrate supply. It is shown here that the GLN1;2 promoter is mainly active in the minor veins of leaves and flowers and, to a lower extent, in the parenchyma of mature leaves. Cytoimmunochemistry reveals that the GLN1;2 protein is present in the companion cells. The role of GLN1;2 was determined by examining the physiology of gln1;2 knockout mutants. Mutants displayed lower glutamine synthetase activity, higher ammonium concentration, and reduced rosette biomass compared with the wild type (WT) under ample nitrate supply only. No difference between mutant and WT can be detected under limiting nitrate conditions. Despite total amino acid concentration was increased in the old leaves of mutants at high nitrate, no significant difference in nitrogen remobilization can be detected using 15N tracing. Growing plants in vitro with ammonium or nitrate as the sole nitrogen source allowed us to confirm that GLN1;2 is induced by ammonium in roots and to observe that gln1;2 mutants displayed, under such conditions, longer root hair and smaller rosette phenotypes in ammonium. Altogether the results suggest that GLN1;2 is essential for nitrogen assimilation under ample nitrate supply and for ammonium detoxification

Facing the urgency of therapies for progressive MS — a Progressive MS Alliance proposal

Therapies for infiltrative inflammation in multiple sclerosis (MS) have advanced greatly, but neurodegeneration and compartmentalized inflammation remain virtually untargeted as in other diseases of the nervous system. Consequently, many therapies are available for the relapsing–remitting form of MS, but the progressive forms remain essentially untreated. The objective of the International Progressive MS Alliance is to expedite the development of effective therapies for progressive MS through new initiatives that foster innovative thinking and concrete advancements. Based on these principles, the Alliance is developing a new funding programme that will focus on experimental medicine trials. Here, we discuss the reasons behind the focus on experimental medicine trials, the strengths and weaknesses of these approaches and of the programme, and why we hope to advance therapies while improving the understanding of progression in MS. We are soliciting public and academic feedback, which will help shape the programme and future strategies of the Alliance

Cerebellar volume as imaging outcome in progressive multiple sclerosis

Background and purpose: To assess whether cerebellar volumes changes could represent a sensitive outcome measure in primary-progressive MS. Material and methods: Changes in cerebellar volumes over one-year follow-up, estimated in 26 primary-progressive MS patients and 20 controls with Freesurfer longitudinal pipeline, were assessed using Wilcoxon test and tested for their correlation with disability worsening by a logistic regression. Clinical worsening was defined as EDSS score increase or change of >20% for 25-foot walk test or 9-hole peg test scores at follow-up. Sample sizes for given treatment effects and power were calculated. The findings were validated in an independent cohort of 20 primary-progressive MS patients. Results: Significant changes were detected in brain T1 lesion volume (p<0.01), cerebellar T2 and T1 lesion volume (p<0.01 and p<0.05), cerebellar volume, cerebellar cortex volume, and cerebellar WM volume (p<0.001). Only cerebellar volume and cerebellar cortex volume percentage change were significantly reduced in clinically progressed patients when compared to patients who did not progress (p<0.01; respectively AUC of 0.91 and 0.96). Cerebellar volume percentage changes were consistent in the exploration and validation cohorts (cerebellar volume -1.90±1.11% vs -1.47±2.30%; cerebellar cortex volume -1.68±1.41% vs -1.56±2.23%). Based on our results the numbers of patients required to detect a 30% effect are 81 per arm for cerebellar volume and 162 per arm for cerebellar cortex volume (90% power, type 1 error alpha = 0.05). Conclusions: Our results suggest a role for cerebellar cortex volume and cerebellar volume as potential short-term imaging metrics to monitor treatment effect in primary-progressive MS clinical trials