Is There a "Right" Charging Principle with the NGN Advent?

Historically, telecommunications services developed adding one network to another (voice and data networks), but Next Generation Networks (NGN) are developing as native multiservice networks. Main characteristics include: broadband capacity, IP protocol, ability to transmit voice, data and video, quality control, separation among different network layers. The fact to deliver with one only network different services such as voice and data, now treated in a very different way with respect to charging principles (interconnection for voice, peering for Internet exchanges), poses the problem of the charging model to adopt in the future. In the paper we will analyse pros and cons of the different charging principles, both at wholesale and retail level, from an economic perspective. The first conclusion is that there is no "magic solution", as any criteria has pros and cons, but that it appears more appropriate to leave operators to choose their retail models, once the wholesale criteria are settled. Then the paper concentrates on the different scenarios which can arise choosing different charging principles at wholesale level. Particular attention is given to the issues of quality safeguard and of recovering nvestments in innovative networks and services. On many aspects "intermediate" scenarios seem better to answer economic problems than the "pure" scenarios, (calling party network pays for all wholesale services, including Internet/data, or bill & keep for everything, including voice).NGN, charging principles.

University language teachers as autonomous learners

The present empirical study investigates how university language teachers approach their own professional development (PD) and which forms their development can take. Research into teacher professional development largely tends to concentrate on school teachers, whereas in this study university language teachers are the focus of interest. Furthermore, the role of teachers’ personal contributions to their own professional learning is the main concern of the study rather than which features of teacher programmes might have a positive impact on teachers’ development. The way the teachers proceed in accomplishing their PD task has been documented through a Grounded Theory approach to data. Questionnaries and follow-up semi-structured qualitative interviews were used to explore the approaches of ten university language teachers. Two professional profiles were identified and were named the 'Learners' and the 'Developers' because they correspond to Vygotsky’s (1978) distinction between learning and development and because this best characterises the teachers' differences in this study. The characteristics of the two profiles centre around their awareness, the way they arrange their learning environment and their attitudinal orientation. The teachers with a “developer”-profile display a high capacity of ‘professional self’-revision, have a highly developed awareness of their own learning concerns and set long-term and demanding professional goals that require them to go beyond routines. They maintain a focused attention on their goals and on the various tasks to pursue them, and are attentive to their positive emotional well-being as teachers as well as to their cognitive needs. One critical result is that they adopt and develop appropriate strategies that lead them to their goals. As a consequence, they enter a cycle of change and ultimately achieve their affective goals. The teachers with a ‘learner’-profile on the contrary are less attentive to all the relevant dimensions involved in their own professional learning. Contrary to the ‘developer’-colleagues, they lack the strategies appropriate for them to realise their goals and to reduce the complexity of the teacher development task. Their personal contribution to their own development is limited, their learning environment is consequently more secure, but less challenging than for the previous profile, and requires less effort on their behalf. Overall, they do not seem to be completely in charge of their own learning and reproduced “traditional” learners’ behaviours. Their attitudes towards their own professional development did not accord with their lifelong learning goals. Their ‘professional self’ could be more intensively developed. The present study aims to complement the existing debate on language teachers’ professionalism and to add new insights on the dynamic way in which teachers make sense of their professional development. Based on the results, it is hoped that a contribution will be made to bridging the gap between research and practice by indicating how to augment existing reflective tools, such as teachers’ portfolios, designed to sustain reflection in language teachers and thus advance their professional development

Hard state neutron star and black hole X-ray binaries in the radio:X-ray luminosity plane

Motivated by the large body of literature around the phenomenological properties of accreting black hole (BH) and neutron star (NS) X-ray binaries in the radio:X-ray luminosity plane, we carry out a comparative regression analysis on 36 BHs and 41 NSs in hard X-ray states, with data over 7 dex in X-ray luminosity for both. The BHs follow a radio to X-ray (logarithmic) luminosity relation with slope $\beta=0.59\pm0.02$, consistent with the NSs' slope ($\beta=0.44^{+0.05}_{-0.04}$) within 2.5$\sigma$. The best-fitting intercept for the BHs significantly exceeds that for the NSs, cementing BHs as more radio loud, by a factor $\sim$22. \This discrepancy can not be fully accounted for by the mass or bolometric correction gap, nor by the NS boundary layer contribution to the X-rays, and is likely to reflect physical differences in the accretion flow efficiency, or the jet powering mechanism. Once importance sampling is implemented to account for the different luminosity distributions, the slopes of the non-pulsating and pulsating NS subsamples are formally inconsistent ($>3\sigma$), unless the transitional millisecond pulsars (whose incoherent radio emission mechanism is not firmly established) are excluded from the analysis. We confirm the lack of a robust partitioning of the BH data set into separate luminosity tracks.Comment: Accepted by MNRAS as a Lette

A ~50,000 solar mass black hole in the nucleus of RGG 118

Scaling relations between black hole (BH) masses and their host galaxy properties have been studied extensively over the last two decades, and point towards co-evolution of central massive BHs and their hosts. However, these relations remain poorly constrained for BH masses below $\sim10^{6}$ M_sun. Here we present optical and X-ray observations of the dwarf galaxy RGG 118 taken with the Magellan Echellette Spectrograph on the 6.5m Clay Telescope and Chandra X-ray Observatory. Based on Sloan Digital Sky Survey spectroscopy, RGG 118 was identified as possessing narrow emission line ratios indicative of photoionization partly due to an active galactic nucleus. Our higher resolution spectroscopy clearly reveals broad H$\alpha$ emission in the spectrum of RGG 118. Using virial BH mass estimate techniques, we calculate a BH mass of $\sim50,000$ \msun. We detect a nuclear X-ray point source in RGG 118, suggesting a total accretion powered luminosity of $L=4\times10^{40}~{\rm erg~s^{-1}}$, and an Eddington fraction of $\sim1$ per cent. The BH in RGG 118 is the smallest ever reported in a galaxy nucleus and we find that it lies on the extrapolation of the $M_{\rm BH}-\sigma_{\ast}$ relation to the lowest masses yet.Comment: Accepted to ApJL. 6 pages, 4 figure

Politique de désignation toponymique

Este artículo surge de un estudio hermenéutico sobre la educación del cuerpo cuyo objeto es analizar las condiciones de sensibilidad en clave pedagógica como ámbito de estudio de la Educación Corporal. En esta investigación se piensa lo sensible en relación con la educación a partir de una ruta filosófica, pedagógica y experiencial, por ello, el estudio de lo sensible se enmarca en el pensamiento filosófico de Federico Nietzsche y Gilles Deleuze, y la educación en la reflexión pedagógica de Jorge Larrosa y Fernando Bárcena. Con el análisis teórico documental que se realiza no se trata de reproducir conceptos ni ideas, sino de analizar aquellas situaciones en que la sensibilidad despliega otras maneras de pensar la educación porque la preocupación por las condiciones de sensibilidad pasa también por la necesidad de ver la estrecha relación que guarda el cuerpo y la Educación. Así, en este texto se exponen algunas prácticas corporales en clave pedagógica para hacer ver las potencias que se ejercen sobre el cuerpo. De conformidad con la dimensión simbólica del cuerpo, las prácticas corporales son, ante todo, simbologías corporales, son modos de decir del cuerpo que nos orientan para pensar una educación de lo sensible. Esta ruta experiencial del danzar, jugar y caminar permite abordar el análisis de la educación y del cuerpo desde experiencias que, quizás, están desposeídas de significado educativo, este modo de preocuparnos por lo pedagógico es una posibilidad para pensar una educación de lo sensible desde el cuerpo

Polarized synchrotron emission in quiescent black hole X-ray transients

We present near-infrared polarimetric observations of the black hole X-ray binaries Swift J1357.2-0933 and A0620-00. In both sources, recent studies have demonstrated the presence of variable infrared synchrotron emission in quiescence, most likely from weak compact jets. For Swift J1357.2-0933 we find that the synchrotron emission is polarized at a level of 8.0 +- 2.5 per cent (a 3.2 sigma detection of intrinsic polarization). The mean magnitude and rms variability of the flux (fractional rms of 19-24 per cent in K_s-band) agree with previous observations. These properties imply a continuously launched (stable on long timescales), highly variable (on short timescales) jet in the Swift J1357.2-0933 system in quiescence, which has a moderately tangled magnetic field close to the base of the jet. We find that for A0620-00, there are likely to be three components to the optical-infrared polarization; interstellar dust along the line of sight, scattering within the system, and an additional source that changes the polarization position angle in the reddest (H and K_s) wave-bands. We interpret this as a stronger contribution of synchrotron emission, and by subtracting the line-of-sight polarization, we measure an excess of ~ 1.25 +- 0.28 per cent polarization and a position angle of the magnetic field vector that is consistent with being parallel with the axis of the resolved radio jet. These results imply that weak jets in low luminosity accreting systems have magnetic fields which possess similarly tangled fields compared to the more luminous, hard state jets in X-ray binaries.Comment: Accepted to MNRA

Microscopic mechanism of protein cryopreservation in an aqueous solution with trehalose

In order to investigate the cryoprotective mechanism of trehalose on proteins, we use molecular dynamics computer simulations to study the microscopic dynamics of water upon cooling in an aqueous solution of lysozyme and trehalose. We find that the presence of trehalose causes global retardation of the dynamics of water. Comparing aqueous solutions of lysozyme with/without trehalose, we observe that the dynamics of water in the hydration layers close to the protein is dramatically slower when trehalose is present in the system. We also analyze the structure of water and trehalose around the lysozyme and find that the trehalose molecules form a cage surrounding the protein that contains very slow water molecules. We conclude that the transient cage of trehalose molecules that entraps and slows the water molecules prevents the crystallisation of protein hydration water upon cooling.DC, EGS, and HES thank the NSF chemistry Division for support (Grants CHE-1213217, CHE-0911389, and CHE-0908218). PG gratefully acknowledges the computational support reveived by the INFN RM3-GRID at Roma Tre University. (CHE-1213217 - NSF chemistry Division; CHE-0911389 - NSF chemistry Division; CHE-0908218 - NSF chemistry Division)Published versio

X-ray and Ultraviolet Properties of AGN in Nearby Dwarf Galaxies

We present new Chandra X-ray Observatory and Hubble Space Telescope observations of eight optically selected broad-line AGN candidates in nearby dwarf galaxies ($z<0.055$). Including archival Chandra observations of three additional sources, our sample contains all ten galaxies from Reines et al. (2013) with both broad H$\alpha$ emission and narrow-line AGN ratios (6 AGNs, 4 Composites), as well as one low-metallicity dwarf galaxy with broad H$\alpha$ and narrow-line ratios characteristic of star formation. All eleven galaxies are detected in X-rays. Nuclear X-ray luminosities range from $L_{0.5-7 \rm{keV}}\approx5\times10^{39}$ to $1\times10^{42}$ $\rm{erg}\rm{s^{-1}}$. In all cases except for the star forming galaxy, the nuclear X-ray luminosities are significantly higher than would be expected from X-ray binaries, providing strong confirmation that AGN and composite dwarf galaxies do indeed host actively accreting BHs. Using our estimated BH masses (which range from $\sim7\times10^{4}-1\times10^{6}~M_{\odot}$), we find inferred Eddington fractions ranging from $\sim0.1-50\%$, i.e. comparable to massive broad-line quasars at higher redshift. We use the HST imaging to determine the ratio of ultraviolet to X-ray emission for these AGN, finding that they appear to be less X-ray luminous with respect to their UV emission than more massive quasars (i.e. $\alpha_{\rm OX}$ values an average of 0.36 lower than expected based on the relation between $\alpha_{\rm OX}$ and $2500{\rm \AA}$ luminosity). Finally, we discuss our results in the context of different accretion models onto nuclear BHs.Comment: 15 pages, 15 figures, 4 tables. Submitted to Ap