245 research outputs found
A Statistical Inference Method for Interpreting the CLASP Observations
On 3rd September 2015, the Chromospheric Lyman-Alpha SpectroPolarimeter
(CLASP) successfully measured the linear polarization produced by scattering
processes in the hydrogen Lyman- line of the solar disk radiation,
revealing conspicuous spatial variations in the and signals. Via
the Hanle effect the line-center and amplitudes encode information
on the magnetic field of the chromosphere-corona transition region (TR), but
they are also sensitive to the three-dimensional structure of this corrugated
interface region. With the help of a simple line formation model, here we
propose a statistical inference method for interpreting the Lyman-
line-center polarization observed by CLASP.Comment: Accepted for publication in The Astrophysical Journa
CLASP Constraints on the Magnetization and Geometrical Complexity of the Chromosphere-Corona Transition Region
The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is a suborbital
rocket experiment that on 3rd September 2015 measured the linear polarization
produced by scattering processes in the hydrogen Ly- line of the solar
disk radiation, whose line-center photons stem from the chromosphere-corona
transition region (TR). These unprecedented spectropolarimetric observations
revealed an interesting surprise, namely that there is practically no
center-to-limb variation (CLV) in the line-center signals. Using an
analytical model, we first show that the geometrical complexity of the
corrugated surface that delineates the TR has a crucial impact on the CLV of
the and line-center signals. Secondly, we introduce a statistical
description of the solar atmosphere based on a three-dimensional (3D) model
derived from a state-of-the-art radiation magneto-hydrodynamic simulation. Each
realization of the statistical ensemble is a 3D model characterized by a given
degree of magnetization and corrugation of the TR, and for each such
realization we solve the full 3D radiative transfer problem taking into account
the impact of the CLASP instrument degradation on the calculated polarization
signals. Finally, we apply the statistical inference method presented in a
previous paper to show that the TR of the 3D model that produces the best
agreement with the CLASP observations has a relatively weak magnetic field and
a relatively high degree of corrugation. We emphasize that a suitable way to
validate or refute numerical models of the upper solar chromosphere is by
confronting calculations and observations of the scattering polarization in
ultraviolet lines sensitive to the Hanle effect.Comment: Accepted for publication in The Astrophysical Journal Letter
The use of antimicrobials in italian heavy pig fattening farms
Data on antimicrobial use (AMU) in heavy pig production (>150 kg) are limited. The aim of this study was to investigate the AMU in this production. Data from 2015 were collected for 143 fattening farms. The AMU was estimated through a treatment index per 100 days (TI100) using the defined daily dose animal for Italy (DDDAit). When possible, a comparison with the European Medicines Agency’s defined daily doses for animals (DDDvet) was performed. The median TI100 was 10.7 (range, 0.2–49.5). Group treatments represented 94.6% of overall consumption. The AMU calculated using DDDAit and DDDvet were strongly correlated (ρ = 0.976; p < 0.001). The AMU was negatively correlated with injectables use (ρ = −0.46, p < 0.001) and positively correlated with oral products (ρ = 0.21, p = 0.014), premixes (ρ = 0.26, p = 0.002), and mortality (ρ = 0.18; p = 0.027). Farm size was negatively correlated with AMU (ρ = −0.29, p < 0.001). Smaller farms were more frequently above the median TI100 (odds ratio = 2.3, 95% confidence interval = 1.2–4.7), suggesting that they may have lower biosecurity and management standards. The results of this study should provide useful insights for the development of an Italian monitoring system
Recent Advances in Chromospheric and Coronal Polarization Diagnostics
I review some recent advances in methods to diagnose polarized radiation with
which we may hope to explore the magnetism of the solar chromosphere and
corona. These methods are based on the remarkable signatures that the
radiatively induced quantum coherences produce in the emergent spectral line
polarization and on the joint action of the Hanle and Zeeman effects. Some
applications to spicules, prominences, active region filaments, emerging flux
regions and the quiet chromosphere are discussed.Comment: Review paper to appear in "Magnetic Coupling between the Interior and
the Atmosphere of the Sun", eds. S. S. Hasan and R. J. Rutten, Astrophysics
and Space Science Proceedings, Springer-Verlag, 200
Magnetic Imaging of the Outer Solar Atmosphere (MImOSA): Unlocking the driver of the dynamics in the upper solar atmosphere
The magnetic activity of the Sun directly impacts the Earth and human life.
Likewise, other stars will have an impact on the habitability of planets
orbiting these host stars. The lack of information on the magnetic field in the
higher atmospheric layers hampers our progress in understanding solar magnetic
activity. Overcoming this limitation would allow us to address four paramount
long-standing questions: (1) How does the magnetic field couple the different
layers of the atmosphere, and how does it transport energy? (2) How does the
magnetic field structure, drive and interact with the plasma in the
chromosphere and upper atmosphere? (3) How does the magnetic field destabilise
the outer solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science questions. We
suggest a suite of three instruments that far exceed current capabilities in
terms of spatial resolution, light-gathering power, and polarimetric
performance: (a) A large-aperture UV-to-IR telescope of the 1-3 m class aimed
mainly to measure the magnetic field in the chromosphere by combining high
spatial resolution and high sensitivity. (b) An extreme-UV-to-IR coronagraph
that is designed to measure the large-scale magnetic field in the corona with
an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30
cm telescope that combines high throughput in the extreme UV with polarimetry
to connect the magnetic measurements of the other two instruments. This mission
to measure the magnetic field will unlock the driver of the dynamics in the
outer solar atmosphere and thereby greatly advance our understanding of the Sun
and the heliosphere.Comment: Submitted to Experimental Astronomy (on 28. Jul. 2020). Based on a
proposal submitted in response to a call for white papers in the Voyage 2050
long-term plan in the ESA science programme. 36 pages, 10 figure
CLASP2: The Chromospheric LAyer Spectro-Polarimeter
A major remaining challenge for heliophysicsis to decipher the magnetic structure of the chromosphere, due to its "large role in defining how energy is transported into the corona and solar wind" (NASA's Heliophysics Roadmap). Recent observational advances enabled by the Interface Region Imaging Spectrometer (IRIS) have revolutionized our view of the critical role this highly dynamic interface between the photosphere and corona plays in energizing and structuring the outer solar atmosphere. Despite these advances, a major impediment to better understanding the solar atmosphere is our lack of empirical knowledge regarding the direction and strength of the magnetic field in the upper chromosphere. Such measurements are crucial to address several major unresolved issues in solar physics: for example, to constrain the energy flux carried by the Alfven waves propagating through the chromosphere (De Pontieuet al., 2014), and to determine the height at which the plasma Beta = 1 transition occurs, which has important consequences for the braiding of magnetic fields (Cirtainet al., 2013; Guerreiroet al., 2014), for propagation and mode conversion of waves (Tian et al., 2014a; Straus et al., 2008) and for non-linear force-free extrapolation methods that are key to determining what drives instabilities such as flares or coronal mass ejections (e.g.,De Rosa et al., 2009). The most reliable method used to determine the solar magnetic field vector is the observation and interpretation of polarization signals in spectral lines, associated with the Zeeman and Hanle effects. Magnetically sensitive ultraviolet spectral lines formed in the upper chromosphere and transition region provide a powerful tool with which to probe this key boundary region (e.g., Trujillo Bueno, 2014). Probing the magnetic nature of the chromosphere requires measurement of the Stokes I, Q, U and V profiles of the relevant spectral lines (of which Q, U and V encode the magnetic field information)
Arachidonic Acid but not Eicosapentaenoic Acid (EPA) and Oleic Acid Activates NF-κB and Elevates ICAM-1 Expression in Caco-2 Cells
In patients with inflammatory bowel disease (IBD), intestinal activation of the transcription factor NF-κB as well as intercellular adhesion molecule (ICAM)-1 expression, which is involved in recruiting leukocytes to the side of inflammation is increased. Moreover, colonic arachidonic acid (ARA) proportions are increased and oleic acid (OA) proportions are decreased. Fish oils are protective in IBD patients however, a side-by-side comparison between effects of fish oils, ARA and OA has not been made. We therefore, compared effects of eicosapentaenoic acid (EPA) versus ARA and OA on ICAM-1 expression in Caco-2 enterocytes. To validate our model we showed that dexamethasone, sulfasalazine and PPARα (GW7647) or PPARγ (troglitazone) agonists significantly lowered ICAM-1 expression. ICAM-1 expression of non-stimulated and cytokine stimulated Caco-2 cells cultured for 22 days with ARA was significant higher as compared to EPA and OA. Furthermore, ARA increased NF-κB activation in a reporter cell-line as compared to EPA. Antibody array analysis of multiple inflammatory proteins particularly showed an increased monocyte chemotactic protein (MCP)-1 and angiogenin production and a decreased interleukin (IL)-6 and IL-10 production by ARA as compared to EPA. Our results showed that ARA but not EPA and OA activates NF-κB and elevates ICAM-1 expression in Caco-2 enterocytes. It suggests that replacement of ARA by EPA or OA in the colon mucosa might have beneficial effects for IBD patients. Finally, we suggest that the pro-inflammatory effects of ARA versus EPA and OA are not related to PPARγ activation and/or eicosanoid formation
Science Requirement Document for the European Solar Telescope
The European Solar Telescope (EST)1 is a research infrastructure for solar physics. It is planned to be an on-axis solar
telescope with an aperture of 4m and equipped with an innovative suite of spectro-polarimetric and imaging post-focus
instrumentation. The EST project was initiated and is driven by EAST2, the European Association for Solar Telescopes.
EAST was founded in 2006 as an association of 14 European countries. Today, as of December 2019, EAST consists of
26 European research institutes from 18 European countries.
The Preliminary Design Phase of EST was accomplished between 2008 and 2011. During this phase, in 2010, the first
version of the EST Science Requirement Document (SRD)was published. After EST became a project on the ESFRI3
roadmap 2016, the preparatory phase started. This phase is partially supported by EU funding through the PRE-EST
H2020 project4. The goal of the preparatory phase is to accomplish a final design for the telescope and the legal governance
structure of EST. A major milestone on this path is to revisit and update the Science Requirement Document
(SRD).
The EST Science Advisory Group (SAG) has been constituted by EAST and the Board of the PRE-EST4 EU project in
November 2017 and has been charged with the task of providing with a final statement on the science requirements for
EST. Based on the conceptual design, the SRD update takes into account recent technical and scientific developments, to
ensure that EST provides significant advancement beyond the current state-of-the-art.
The present update of the EST SRD has been developed and discussed during a series of EST SAG meetings:
1st telecon meeting on Nov 5th, 2017
2nd meeting in Freiburg, Nov 24, 2017
3rd telecon meeting, Dec 15, 2017
4th telecon meeting, March 26, 2018
5th meeting in Belfast, April 16 & 17, 2018
6th meeting in Naxos, June 16, 2018
7th telecon meeting, January 14, 2019
8th telecon meeting, October 11, 2019
9th telecon meeting, October 22, 2019
10th telecon meeting, December 3, 2019
The SRD develops the top-level science objectives of EST into individual science cases. Identifying critical science
requirements is one of its main goals. Those requirements will define the capabilities of EST and the post-focus instrument
suite. The technical requirements for the final design of EST will be derived from the SRD.
The science cases presented in Part II (Sects. 1 to 8) are not intended to cover all the science questions to be addressed
with EST, but rather to provide a precise overview of the capabilities that will make of EST a competitive state-of-the-art
telescope to push the boundaries of our knowledge over the next few decades. The science cases contain detailed observing
programmes specifying the type of observations needed to solve specific science problems. An eort is being made to
define the parameters of the required observations as accurately as possible, taking into account both present capabilities
and technological developments expected in the near future. The tables of the observing programmes corresponding to
the science cases are compiled in Sect. 10. The EST science cases represent challenging observations that put strong
constraints on the telescope and its instrument suite. Ultimately, they will be translated into Technical Requirement
Document (TRD) leading to the final EST design to be implemented during the construction phase.
The unique design advantages of the EST concept is presented in Section 11. The eect of the science cases on the EST
design are discussed in Section 12 and summarized in Section 13.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 739 50
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