O stars effective temperature and HII regions ionization parameter gradients in the Galaxy

Extensive photoionization model grids are computed for single star HII regions using stellar atmosphere models from the WM-basic code. Mid-IR emission line intensities are predicted and diagnostic diagrams of [NeIII]/[NeII] and [SIV]/[SIII] excitation ratio are build, taking into account the metallicities of both the star and the HII region. The diagrams are used in conjunction with galactic HII region observations obtained with the ISO Observatory to determine the effective temperature Teff of the exciting O stars and the mean ionization parameter U. Teff and U are found to increase and decrease, respectively, with the metallicity of the HII region represented by the [Ne/Ne_sol] ratio. No evidence is found for gradients of Teff or U with galactocentric distance Rgal. The observed excitation sequence with Rgal is mainly due to the effect of the metallicity gradient on the spectral ionizing shape, upon which the effect of an increase in Teff with Z is superimposed. We show that not taking properly into account the effect of metallicity on the ionizing shape of the stellar atmosphere would lead to an apparent decrease of Teff with Z and an increase of Teff with Rgal.Comment: Accepted in Ap

A Consistent Spectral Model of WR 136 and its Associated Bubble NGC 6888

We analyse whether a stellar atmosphere model computed with the code CMFGEN provides an optimal description of the stellar observations of WR 136 and simultaneously reproduces the nebular observations of NGC 6888, such as the ionization degree, which is modelled with the pyCloudy code. All the observational material available (far and near UV and optical spectra) were used to constrain such models. We found that even when the stellar luminosity and the mass-loss rate were well constrained, the stellar temperature T_* at tau = 20, can be in a range between 70 000 and 110 000 K. When using the nebula as an additional restriction we found that the stellar models with T_* \sim 70 000 K represent the best solution for both, the star and the nebula. Results from the photoionization model show that if we consider a chemically homogeneous nebula, the observed N^+/O^+ ratios found in different nebular zones can be reproduced, therefore it is not necessary to assume a chemical inhomogeneous nebula. Our work shows the importance of calculating coherent models including stellar and nebular constraints. This allowed us to determine, in a consistent way, all the physical parameters of both the star and its associated nebula. The chemical abundances derived are 12 + log(N/H) = 9.95, 12 + log(C/H) = 7.84 and 12 + log(O/H) = 8.76 for the star and 12 + log(N/H) = 8.40, 12 + log(C/H) = 8.86 and 12 + log(O/H) = 8.20. Thus the star and the nebula are largely N- and C- enriched and O-depleted.Comment: 17 pages, 8 figures, 8 tables; MNRAS accepte

Modelling of aspherical nebulae. I. A quick pseudo-3D photoionization code

We describe a pseudo-3D photoionization code, NEBU_3D and its associated visualization tool, VIS_NEB3D, which are able to easily and rapidly treat a wide variety of nebular geometries, by combining models obtained with a 1D photoionization code. The only requirement for the code to work is that the ionization source is uniqu e and not extended. It is applicable as long as the diffuse ionizing radiation f ield is not dominant and strongly inhomogeneous. As examples of the capabilities of these new tools, we consider two very differ ent theoretical cases. One is that of a high excitation planetary nebula that ha s an ellipsoidal shape with two polar density knots. The other one is that of a blister HII region, for which we have also constructed a spherical model (the sp herical impostor) which has exactly the same Hbeta surface brightness distrib ution as the blister model and the same ionizing star. These two examples warn against preconceived ideas when interpreting spectroscop ic and imaging data of HII regions and planetary nebulae. The tools NEBU_3D and VIS_NEB3D, which will be made publicly available in the future, should facilitat e the performance of numerical experiments, to yield a better understanding of t he physics of aspherical ionized nebulae.Comment: 11 pages, 19 figures (mainly in color). Accepted by MNRA

Policy-based access control from numerical evidence

Increasingly, access to resources needs to be regulated or informed by considerations such as risk, cost, and reputation. We therefore propose a framework for policy languages, based on semi-rings, that aggregate quantitative evidence to support decision-making in access control systems. As aggregation operators \addition", \worst case", and \best case" over non- negative reals are both relevant in practice and amenable to analysis, we study an instance, Peal, of our framework in that setting. Peal is a stand-alone policy language but can also be integrated with existing policy languages. Peal policies can be synthesized into logical formulae that no longer make reference to quantities but capture all policy behavior. Satis ability checking of such formulae can be used to validate and analyze policies in this new evidence-based approach. We discuss a number of applications, including vacuity, redundancy, change-impact and safety analysis. The synthesis algorithm requires a form of subset enumeration, for which we develop bespoke algorithms and demonstrate experimentally that our algorithms work better than generic state exploration methods. We also sketch how our approach extends from non-negative reals to other semi-rings and even to rings such as the real numbers

cyberaCTIve: a STIX-based Tool for Cyber Threat Intelligence in Complex Models

Cyber threat intelligence (CTI) is practical real-world information that is collected with the purpose of assessing threats in cyber-physical systems (CPS). A practical notation for sharing CTI is STIX. STIX offers facilities to create, visualise and share models; however, even a moderately simple project can be represented in STIX as a quite complex graph, suggesting to spread CTI across multiple simpler sub-projects. Our tool aims to enhance the STIX-based modelling task in contexts when such simplifications are infeasible. Examples can be the microgrid and, more in general, the smart grid.Comment: 11 pages, 8 figures, technical repor

Galactic Planetary Nebulae with Wolf-Rayet Nuclei III. Kinematical Analysis of a Large Sample of Nebulae

Expansion velocities (Vexp) of different ions and line widths at the base of the lines are measured and analyzed for 24 PNe with [WC]-type nuclei (WRPNe), 9 PNe ionized by WELS (WLPNe) and 14 ordinary PNe. A comparative study of the kinematical behavior of the sample clearly demonstrates that WRPNe have in average 40-45% larger Vexp, and possibly more turbulence than WLPNe and ordinary PNe. WLPNe have velocity fields very much alike the ones of ordinary PNe, rather than the ones of WRPNe. All the samples (WRPNe, WLPNe and ordinary PNe) show expansion velocities increasing with age indicators, for example is larger for low-density nebulae and also it is larger for nebulae around high-temperature stars. This age effect is much stronger for evolved WRPNe, suggesting that the [WC] winds have been accelerating the nebulae for a long time, while for non-WRPNe the acceleration seems to stop at some point when the star reaches a temperature of about 90,000-100,000 K. Non-WR nebulae reach a maximum Vexp < 30 km/s while evolved WRPNe reach maximum Vexp of about 40 km/s. For all kind of objects (WRPNe and non-WRPNe) it is found that in average Vexp(N+) is slightly larger than Vexp(O++), indicating that the nebulae present acceleration of the external shells.Comment: 20 pages, 11 fig. To appear in Revista Mexicana de Astronomia y Astrofisica, April 200

Photoionization models of the CALIFA HII regions. I. Hybrid models

Photoionization models of HII regions require as input a description of the ionizing SED and of the gas distribution, in terms of ionization parameter U and chemical abundances (e.g. O/H and N/O). A strong degeneracy exists between the hardness of the SED and U, which in turn leads to high uncertainties in the determination of the other parameters, including abundances. One way to resolve the degeneracy is to fix one of the parameters using additional information. For each of the ~ 20000 sources of the CALIFA HII regions catalog, a grid of photoionization models is computed assuming the ionizing SED being described by the underlying stellar population obtained from spectral synthesis modeling. The ionizing SED is then defined as the sum of various stellar bursts of different ages and metallicities. This solves the degeneracy between the shape of the ionizing SED and U. The nebular metallicity (associated to O/H) is defined using the classical strong line method O3N2 (which gives to our models the status of "hybrids"). The remaining free parameters are the abundance ratio N/O and the ionization parameter U, which are determined by looking for the model fitting [NII]/Ha and [OIII]/Hb. The models are also selected to fit [OII]/Hb. This process leads to a set of ~ 3200 models that reproduce simultaneously the three observations. We find that the regions associated to young stellar bursts suffer leaking of the ionizing photons, the proportion of escaping photons having a median of 80\%. The set of photoionization models satisfactorily reproduces the electron temperature derived from the [OIII]4363/5007 line ratio. We determine new relations between the ionization parameter U and the [OII]/[OIII] or [SII]/[SIII] line ratios. New relations between N/O and O/H and between U and O/H are also determined. All the models are publicly available on the 3MdB database.Comment: Accepted for publication in A&

Challenges recruiting to a proof-of-concept pharmaceutical trial for a rare disease: The trigeminal neuralgia experience

Background: This study aimed to describe recruitment challenges encountered during a phase IIa study of vixotrigine, a state and use-dependent Nav1.7 channel blocker, in individuals with trigeminal neuralgia. Methods: This was an international, multicenter, placebo-controlled, randomized withdrawal study that included a 7-day run-in period, a 21-day open-label phase, and a 28-day double-blind phase in which patients (planned n = 30) were randomized to vixotrigine or placebo. Before recruitment, all antiepileptic drugs had to be stopped, except for gabapentin or pregabalin. After the trial, patients returned to their original medications. Patient recruitment was expanded beyond the original five planned (core) centers in order to meet target enrollment (total recruiting sites N = 25). Core sites contributed data related to patient identification for study participation (prescreening data). Data related to screening failures and study withdrawal were also analyzed using descriptive statistics. Results: Approximately half (322/636; 50.6%) of the patients who were prescreened at core sites were considered eligible for the study and 56/322 (17.4%) were screened. Of those considered eligible, 26/322 (8.1%) enrolled in the study and 6/322 (1.9%) completed the study. In total, 125 patients were screened across all study sites and 67/125 (53.6%) were enrolled. At prescreening, reasons for noneligibility varied by site and were most commonly diagnosis change (78/314; 24.8%), age &gt; 80 years (75/314; 23.9%), language/distance/mobility (61/314; 19.4%), and noncardiac medical problems (53/314; 16.9%). At screening, frequently cited reasons for noneligibility included failure based on electrocardiogram, insufficient pain, and diagnosis change. Conclusions: Factors contributing to recruitment challenges encountered in this study included diagnosis changes, anxiety over treatment changes, and issues relating to distance, language, and mobility. Wherever possible, future studies should be designed to address these challenges. Trial registration: ClinicalTrials.gov, NCT01540630. EudraCT, 2010-023963-16. 07 Aug 2015