Quiet Sun Magnetic Field Measurements Based on Lines with Hyperfine Structure

The Zeeman pattern of MnI lines is sensitive to hyperfine structure (HFS) and, they respond to hG magnetic field strengths differently from the lines used in solar magnetometry. This peculiarity has been employed to measure magnetic field strengths in quiet Sun regions. However, the methods applied so far assume the magnetic field to be constant in the resolution element. The assumption is clearly insufficient to describe the complex quiet Sun magnetic fields, biasing the results of the measurements. We present the first syntheses of MnI lines in realistic quiet Sun model atmospheres. The syntheses show how the MnI lines weaken with increasing field strength. In particular, kG magnetic concentrations produce NnI 5538 circular polarization signals (Stokes V) which can be up to two orders of magnitude smaller than the weak magnetic field approximation prediction. Consequently, (1) the polarization emerging from an atmosphere having weak and strong fields is biased towards the weak fields, and (2) HFS features characteristic of weak fields show up even when the magnetic flux and energy are dominated by kG fields. For the HFS feature of MnI 5538 to disappear the filling factor of kG fields has to be larger than the filling factor of sub-kG fields. Stokes V depends on magnetic field inclination according to the simple consine law. Atmospheres with unresolved velocities produce asymmetric line profiles, which cannot be reproduced by simple one-component model atmospheres. The uncertainty of the HFS constants do not limit the use of MnI lines for magnetometry.Comment: Accepted for publication in ApJ. 10 pages, 14 figure

Acceleration of weakly collisional solar-type winds

One of the basic properties of the solar wind, that is the high speed of the fast wind, is still not satisfactorily explained. This is mainly due to the theoretical difficulty of treating weakly collisional plasmas. The fluid approach implies that the medium is collision dominated and that the particle velocity distributions are close to Maxwellians. However the electron velocity distributions observed in the solar wind depart significantly from Maxwellians. Recent kinetic collisionless models (called exospheric) using velocity distributions with a suprathermal tail have been able to reproduce the high speeds of the fast solar wind. In this letter we present new developments of these models by generalizing them over a large range of corona conditions. We also present new results obtained by numerical simulations that include collisions. Both approaches calculate the heat flux self-consistently without any assumption on the energy transport. We show that both approaches - the exospheric and the collisional one - yield a similar variation of the wind speed with the basic parameters of the problem; both produce a fast wind speed if the coronal electron distribution has a suprathermal tail. This suggests that exospheric models contain the necessary ingredients for the powering of a transonic stellar wind, including the fast solar one.Comment: Accepted for publication in The Astrophysical Journal Letters (accepted: 13 May 2005

Modelling the incomplete Paschen-Back effect in the spectra of magnetic Ap stars

We present first results of a systematic investigation of the incomplete Paschen-Back effect in magnetic Ap stars. A short overview of the theory is followed by a demonstration of how level splittings and component strengths change with magnetic field strength for some lines of special astrophysical interest. Requirements are set out for a code which allows the calculation of full Stokes spectra in the Paschen-Back regime and the behaviour of Stokes I and V profiles of transitions in the multiplet 74 of FeII is discussed in some detail. It is shown that the incomplete Paschen-Back effect can lead to noticeable line shifts which strongly depend on total multiplet strength, magnetic field strength and field direction. Ghost components (which violate the normal selection rule on J) show up in strong magnetic fields but are probably unobservable. Finally it is shown that measurements of the integrated magnetic field modulus $H_s$ are not adversely affected by the Paschen-Back effect, and that there is a potential problem in (magnetic) Doppler mapping if lines in the Paschen-Back regime are treated in the Zeeman approximation.Comment: 8 pages, 10 figures, to appear in MNRA

Broad band time-resolved E_{p,i}--L_{iso} correlation in GRBs

We report results of a systematic study of the broad band (2--2000 keV) time resolved prompt emission spectra of a sample of gamma-ray bursts (GRBs) detected with both Wide Field Cameras on board the \sax\ satellite and the \batse\ experiment on board CGRO. In this first paper, we study the time-resolved dependence of the intrinsic peak energy $E_{p,i}$ of the $E F(E)$ spectrum on the corresponding isotropic bolometric luminosity $L_{\rm iso}$. The $E_{p,i}$--$L_{\rm iso}$ relation or the equivalent relation between $E_{p,i}$ and the bolometric released energy $E_{iso}$, derived using the time averaged spectra of long GRBs with known redshift, is well established, but its physical origin is still a subject of discussion. In addition, some authors maintain that these relations are the result of instrumental selection effects. We find that not only a relation between the measured peak energy $E_p$ and the corresponding energy flux, but also a strong $E_{p,i}$ versus $L_{\rm iso}$ correlation are found within each burst and merging together the time resolved data points from different GRBs. We do not expect significant instrumental selection effects that can affect the obtained results, apart from the fact that the GRBs in our sample are sufficiently bright to perform a time-resolved spectroscopy and that they have known redshift. If the fundamental physical process that gives rise to the GRB phenomenon does not depend on its brightness, we conclude that the found $E_{p,i}$ versus $L_{\rm iso}$ correlation within each GRB is intrinsic to the emission process, and that the correlations discovered by Amati et al. and Yonetoku et al. are likely not the result of selection effects. We also discuss the properties of the correlations found.Comment: 27 pages,4 tables, 7 figure, accepted for publication in The Astrophysical Journa

Towards a Powerful Hardware‐in‐the‐Loop System for Virtual Calibration of an Off‐Road Diesel Engine

A common challenge among internal combustion engine (ICE) manufacturers is shorten-ing the development time while facing requirements and specifications that are becoming more complex and border in scope. Virtual simulation and calibration are effective instruments in the face of these demands. This article presents the development of zero‐dimensional (0D)—real‐time engine and exhaust after‐treatment system (EAS) models and their deployment on a Virtual test bench (VTB). The models are created using a series of measurements acquired in a real test bench, carefully performed in view of ensuring the highest reliability of the models themselves. A zero‐dimensional approach was chosen to guarantee that models could be run in real‐time and interfaced to the real engine Electronic Control Unit (ECU). Being physically based models, they react to changes in the ECU calibration parameters. Once the models are validated, they are then integrated into a Sim-ulink® based architecture with all the Inputs/Outputs connections to the ECU. This Simulink® model is then deployed on a Hardware in the Loop (HiL) machine for ECU testing and calibration. The results for engine and EAS performance and emissions align with both steady‐state and transient measurements. Finally, two different applications of the HiL system are presented to explain the opportunities and advantages of this tool integrated within the standard engine development. Ex-amples cited refer to altitude calibration activities and soot loading investigation on vehicle duty cycles. The cases described in this work are part of the actual development of one of the latest engines developed by Kohler Engines: the KDI 1903 TCR Stage V. The application of this methodology reveals a great potential for engine development and may become an essential tool for calibration engineers

Broadband X-ray spectrum of the newly discovered broad line radio galaxy IGR J21247+5058

In this paper we present radio and high energy observations of the INTEGRAL source IGR J21247+5058, a broad line emitting galaxy obscured by the Galactic plane. Archival VLA radio data indicate that IGR J21247+5058 can be classified as an FRII Broad Line Radio Galaxy. The spectrum between 610 MHz and 15 GHz is typical of synchrotron self-absorbed radiation with a peak at 8 GHz and a low energy turnover; the core fraction is 0.1 suggestive of a moderate Doppler boosting of the base of the jet. The high energy broad-band spectrum was obtained by combining XMM-Newton and Swift/XRT observation with INTEGRAL/IBIS data. The 0.4-100 keV spectrum is well described by a power law, with slope $\Gamma$=1.5, characterised by complex absorption due to two layers of material partially covering the source and a high energy cut-off around 70-80 keV. Features such as a narrow iron line and a Compton reflection component, if present, are weak, suggesting that reprocessing of the power law photons in the accretion disk plays a negligible role in the source.Comment: 7 pages, 7 figures, 3 tables, accepted for pubblication on MNRA

Line intensity enhancements in stellar coronal X-ray spectra due to opacity effects

Context. The I(15.01 A)/I(16.78 A) emission line intensity ratio in Fe XVII has been reported to deviate from its theoretical value in solar and stellar X-ray spectra. This is attributed to opacity in the 15.01 A line, leading to a reduction in its intensity, and was interpreted in terms of a geometry in which the emitters and absorbers are spatially distinct. Aims. We study the I(15.01 A)/I(16.78 A) intensity ratio for the active cool dwarf EV Lac, in both flare and quiescent spectra. Methods. The observations were obtained with the Reflection Grating Spectrometer on the XMM-Newton satellite. The emission measure distribution versus temperature reconstruction technique is used for our analysis. Results. We find that the 15.01 A line exhibits a significant enhancement in intensity over the optically thin value. To our knowledge, this is the first time that such an enhancement has been detected on such a sound statistical basis. We interpret this enhancement in terms of a geometry in which the emitters and absorbers are not spatially distinct, and where the geometry is such that resonant pumping of the upper level has a greater effect on the observed line intensity than resonant absorption in the line-of-sight.Comment: accepted for publication in A&

Secondary metabolites and eco-friendly techniques for agricultural weed/pest management

In agro-ecosystems, pests (insects, weeds, and other plant’s parasites) compete with crops for edaphic resources, negatively affecting quality and crop yields [1]. Nowadays, synthetic pesticides, easy to apply and accessible to farmers, are the most common and effective methods for pest management [2]. Nevertheless, the negative impact of these chemicals on the environment, human health, and the development of herbicides/pesticides-resistance are shifting the attention to alternative pest control technologies based on natural compounds [3–6]. Therefore, new eco-friendly agronomic techniques and the use of natural or natural-like molecules might represent a valid alternative strategy for pest control in the framework of sustainable agriculture [7–9]. The Special Issue “Secondary metabolites and eco-friendly techniques for agricultural weed/pest management” is timely and could offer interesting contributions to readers on the most recent aspects related to this pivotal topic. It includes 12 research papers (11 original articles and a scientific review) in which different aspects of pest management, from basic research to potential practical approaches, have been investigated through the latest and innovative technologies

Physical Activity and Mortality in Frail, Community-Living Elderly Patients

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