The spectacular X-ray echo of a magnetar burst

The Anomalous X-ray Pulsar (AXP) 1E 1547.0-5408 reactivated in 2009 January with the emission of dozens of short bursts. Follow-up observations with Swift/XRT and XMM-Newton showed the presence of multiple expanding rings around the position of the AXP. These rings are due to scattering, by different layers of interstellar dust, of a very high fluence burst emitted by 1E 1547.0-5408 on 2009 January 22. Thanks to the exceptional brightness of the X-ray rings, we could carry out a detailed study of their spatial and spectral time evolution until 2009 February 4. This analysis gives the possibility to estimate the distance of 1E 1547.0-5408. We also derived constraints on the properties of the dust and of the burst responsible for this rare phenomenon.Comment: Proceedings of the conference X-Ray Astronomy 2009, Present Status, multiwavelength approach and future perspectives, September 7 - 11, 2009, Bologna, Ital

Statistical model for intermittent plasma edge turbulence

The Probability Distribution Function of plasma density fluctuations at the edge of fusion devices is known to be skewed and strongly non-Gaussian. The causes of this peculiar behaviour are, up to now, largely unexplored. On the other hand, understanding the origin and the properties of edge turbulence is a key issue in magnetic fusion research. In this work we show that a stochastic fragmentation model, already successfully applied to fluid turbulence, is able to predict an asymmetric distribution that closely matches experimental data. The asymmetry is found to be a direct consequence of intermittency. A discussion of our results in terms of recently suggested BHP universal curve [S.T. Bramwell, P.C.W. Holdsworth, J.-F. Pinton, Nature (London) 396, 552 (1998)], that should hold for strongly correlated and critical systems, is also proposedComment: 13 pages. Physica Review E, accepte

Behind the dust curtain: the spectacular case of GRB 160623A

We report on the X-ray dust-scattering features observed around the afterglow of the gamma ray burst GRB 160623A. With an XMM-Newton observation carried out ~2 days after the burst, we found evidence of at least six rings, with angular size expanding between ~2 and 9 arcmin, as expected for X-ray scattering of the prompt GRB emission by dust clouds in our Galaxy. From the expansion rate of the rings, we measured the distances of the dust layers with extraordinary precision: 528.1 +\- 1.2 pc, 679.2 +\- 1.9 pc, 789.0 +\- 2.8 pc, 952 +\- 5 pc, 1539 +\- 20 pc and 5079 +\- 64 pc. A spectral analysis of the ring spectra, based on an appropriate dust-scattering model (BARE-GR-B from Zubko et al. 2004}) and the estimated burst fluence, allowed us to derive the column density of the individual dust layers, which are in the range 7x10^20-1.5x10^22 cm^-2. The farthest dust-layer (i.e. the one responsible for the smallest ring) is also the one with the lowest column density and it is possibly very extended, indicating a diffuse dust region. The properties derived for the six dust-layers (distance, thickness, and optical depth) are generally in good agreement with independent information on the reddening along this line of sight and on the distribution of molecular and atomic gas.Comment: 9 pages, 10 figures, 1 table; accepted for publication in MNRA

New application of open source data and Rock Engineering System for debris flow susceptibility analysis

This research describes a quantitative, rapid, and low-cost methodology for debris flow susceptibility evaluation at the basin scale using open-access data and geodatabases. The proposed approach can aid decision makers in land management and territorial planning, by first screening for areas with a higher debris flow susceptibility. Five environmental predisposing factors, namely, bedrock lithology, fracture network, quaternary deposits, slope inclination, and hydrographic network, were selected as independent parameters and their mutual interactions were described and quantified using the Rock Engineering System (RES) methodology. For each parameter, specific indexes were proposed, aiming to provide a final synthetic and representative index of debris flow susceptibility at the basin scale. The methodology was tested in four basins located in the Upper Susa Valley (NW Italian Alps) where debris flow events are the predominant natural hazard. The proposed matrix can represent a useful standardized tool, universally applicable, since it is independent of type and characteristic of the basin

Weakly Admissible Meshes and Discrete Extremal Sets

We present a brief survey on (Weakly) Admissible Meshes and corresponding Discrete Extremal Sets, namely Approximate Fekete Points and Discrete Leja Points. These provide new computational tools for polynomial least squares and interpolation on multidimensional compact sets, with different applications such as numerical cubature, digital filtering, spectral and high-order methods for PDEs

Evidence for a Photospheric Component in the Prompt Emission of the Short GRB120323A and its Effects on the GRB Hardness-Luminosity Relation

The short GRB 120323A had the highest flux ever detected with the Fermi/GBM. Here we study its remarkable spectral properties and their evolution using two spectral models: (i) a single emission component scenario, where the spectrum is modeled by the empirical Band function, and (ii) a two component scenario, where thermal (Planck-like) emission is observed simultaneously with a non-thermal component (a Band function). We find that the latter model fits the integrated burst spectrum significantly better than the former, and that their respective spectral parameters are dramatically different: when fit with a Band function only, the Epeak of the event is unusually soft for a short GRB, while adding a thermal component leads to more typical short GRB values. Our time-resolved spectral analysis produces similar results. We argue here that the two-component model is the preferred interpretation for GRB 120323A, based on: (i) the values and evolution of the Band function parameters of the two component scenario, which are more typical for a short GRB, and (ii) the appearance in the data of a significant hardness-intensity correlation, commonly found in GRBs, when we employee two-component model fits; the correlation is non-existent in the Band-only fits. GRB 110721A, a long burst with an intense photospheric emission, exhibits the exact same behavior. We conclude that GRB 120323A has a strong photospheric emission contribution, first time observed in a short GRB. Magnetic dissipation models are difficult to reconcile with these results, which instead favor photospheric thermal emission and fast cooling synchrotron radiation from internal shocks. Finally, we derive a possibly universal hardness-luminosity relation in the source frame using a larger set of GRBs L,i=(1.59+/-0.84).10^50 (Epeak,i)^(1.33+/-0.07) erg/s), which could be used as a possible redshift estimator for cosmology.Comment: 27 pages, 13 figures, Accepted by ApJ (April, 7th 2013

Effects of Douglas fir stand age on soil chemical properties, nutrient dynamics, and enzyme activity: A case study in Northern Apennines, Italy

The aim of this study was to determine the effect of a Douglas fir plantation along a stand chronosequence in the North Apennine (Italy) on soil carbon and nitrogen stocks, as well as on soil chemical and biochemical properties involved in the nutrients biogeochemical cycle. In 2014, three sites of Douglas fir stands, aged 80, 100, and 120 years, were selected in Vallombrosa forest to study the dynamics of soil nutrients in the ecosystem. Along the Douglas fir chronosequence, general evidence of surface element accumulation was found, including a conspicuous increase of alkaline element with respect to Al, which was attributed to the increase of soil pH along the Douglas fir stand age classes. A general increase of specific enzyme activity (per unit of organic carbon) and functional diversity were observed in the epipedon of the Douglas fir stand over 100 years of age. Moreover, the (chitinase + leucine aminopeptidase) to acid phosphatase ratio progressively increased from 0.15 to 0.31 in the epipedon of the chrononsequence, while the -glucosidase to (chitinase + leucine aminopeptidase) ratio decreased from 1.45 to 0.83, suggesting nitrogen limitation with respect to carbon. In fact, the soil carbon stock progressively increased along the chronosequence, in the epipedon from 17 to 53 Mg C ha(-1) and in the endopedon from 17 to 37 Mg C ha(-1). Conversely, the soil nitrogen stock increased from 1.2 to 2.4 Mg N ha(-1), but not over the 100-year-old stand class. In conclusion, soil organic matter accumulation became sufficient to define the umbric horizon in the Northern Apennines when the Douglas fir plantation reached the age of 100 years. Over this age class of plants, a limitation of soil nitrogen may occur, affecting enzyme activities regulating the biogeochemical cycle of nutrients

Metabolites from marine microorganisms, micro, and macroalgae: Immense scope for pharmacology

Marine organisms produce a large array of natural products with relevance in drug discovery. These compounds have biological activities such as antioxidant, antibacterial, antitumor, antivirus, anticoagulant, anti-in\ufb02ammatory, antihypertensive, antidiabetic, and so forth. Consequently, several of the metabolites have made it to the advanced stages of clinical trials, and a few of them are commercially available. In this review, novel information on natural products isolated from marine microorganisms, microalgae, and macroalgae are presented. Given due research impetus, these marine metabolites might emerge as a new wave of promising drugs

Microturbulence studies in RFX-mod

Present-days Reversed Field Pinches (RFPs) are characterized by quasi-laminar magnetic configurations in their core, whose boundaries feature sharp internal transport barriers, in analogy with tokamaks and stellarators. The abatement of magnetic chaos leads to the reduction of associated particle and heat transport along wandering field lines. At the same time, the growth of steep temperature gradients may trigger drift microinstabilities. In this work we summarize the work recently done in the RFP RFX-mod in order to assess the existence and the impact upon transport of such electrostatic and electromagnetic microinstabilities as Ion Temperature Gradient (ITG), Trapped Electron Modes (TEM) and microtearing modes.Comment: Work presented at the 2010 Varenna workshop "Theory of Fusion Plasmas". To appear in Journal of Physics Conference Serie