Temporal evolution of oscillating coronal loops

Context. Transverse oscillations of coronal structures are currently intensively studied to explore the associated magnetohydrodynamic wave physics and perform seismology of the local medium. Aims. We make a first attempt to measure the thermodynamic evolution of a sample of coronal loops that undergo decaying kink oscillations in response to an eruption in the corresponding active region. Methods. Using data from the six coronal wavelengths of SDO/AIA, we performed a differential emission measure (DEM) analysis of 15 coronal loops before, during, and after the eruption and oscillation. Results. We find that the emission measure, temperature, and width of the DEM distribution undergo significant variations on time scales relevant for the study of transverse oscillations. There are no clear collective trends of increases or decreases for the parameters we analysed. The strongest variations of the parameters occur during the initial perturbation of the loops, and the influence of background structures may also account for much of this variation. Conclusions. The DEM analysis of oscillating coronal loops in erupting active regions shows evidence of evolution on time scales important for the study of the oscillations. Further work is needed to separate the various observational and physical mechanisms that may be responsible for the variations in temperature, DEM distribution width, and total emission measure.Comment: Accepted in A&

Packed hybrid silica nanoparticles as sorbents with thermo-switchable surface chemistry and pore size for fast extraction of environmental pollutants

Thermoresponsive poly(N-isopropylacrylamide)-grafted silica nanoparticles (SiNPs) have been synthesized and fully characterized by ATR-FTIR, TGA, HRTEM, BET and DLS analysis. Hybrid solid phase extraction (SPE) beds with tuneable pore size and switchable surface chemistry were prepared by packing the polymergrafted nanoparticles inside SPE cartridges. The cartridges were tested by checking the thermoregulated elution of model compounds, namely methylene blue, caffeine and amoxicillin. Extraction of the analytes and regeneration of the interaction sites on the sorbent surface was carried out entirely in water solution by changing the external temperature below and above the lower critical solution temperature (LCST) of the polymer. The results demonstrate that the elution of model compounds depends on the temperature-regulated size of the inter-particle voids and on the change of surface properties of the PNIPAM-grafted nanoparticles from hydrophilic to hydrophobic

SQUARE CONCRETE SECTION CONFINED BY FRP: ULTIMATE STRENGTH PREDICTION

ABSTRACT During the last ten years, several studies have been devoted to understanding the behaviour of circular concrete sections confined by FRP. Less studies have dealt with square and rectangular sections, even if the problem is equally important, given the large amount of buildings with such sections that need to be retrofitted due to poor performance under vertical and horizontal actions. A numerical model was already proposed for the prediction of the stress-strain relationship. In order to implement such model in a design code framework, a mechanics-based equation has been developed and preliminary results are presented for the prediction of the ultimate strength of square sections confined by FRP. Since the model considers the corner radius influence, circular sections are automatically included as a particular case. The simplified model has been calibrated by means of a set of experimental values available in the literature

Oscillations of cometary tails: a vortex shedding phenomenon?

Context. During their journey to perihelion, comets may appear in the field-of-view of space-borne optical instruments, showing in some cases a nicely developed plasma tail extending from their coma and exhibiting an oscillatory behaviour. Aims. The oscillations of cometary tails may be explained in terms of vortex shedding because of the interaction of the comet with the solar wind streams. Therefore, it is possible to exploit these oscillations in order to infer the value of the Strouhal number $St$, which quantifies the vortex shedding phenomenon, and the physical properties of the local medium. Methods. We used the Heliospheric Imager (HI) data of the Solar TErrestrial Relations Observatory (STEREO) mission to study the oscillations of the tails of the comets 2P/Encke and C/2012 S1 (ISON) during their perihelion in Nov 2013, determining the Strouhal numbers from the estimates of the halo size, the relative speed of the solar wind flow and the period of the oscillations. Results. We found that the estimated Strouhal numbers are very small, and the typical value of $St\sim0.2$ would be extrapolated for size of the halo larger than $\sim10^6$ km. Conclusions. Despite the vortex shedding phenomenon has not been unambiguously revealed, the findings suggest that some MHD instability process is responsible for the observed behaviour of cometary tails, which can be exploited for probing the physical conditions of the near-Sun region.Comment: 10 pages, 9 figures, accepted for publication in A&A, Sect. 1

Pigs’ husbandry as case study to test effects of vegetable residues’ hydrolysates on animals

Soluble biopolymers (SBO) are research products obtained from alkaline hydrolysis of municipal and agriculture bio-residues. They contain a mix of soluble macromolecules with different C types and functional groups. These features make SBO multipurpose products for the chemical industry, agriculture and animal husbandry. As such, they may contribute to the development of bio-based circular economy by recycling renewable carbon over urban and agriculture environments. To foster production and commercialization, assessment of SBO’s compliance with countries’ regulations is mandatory. The authors performed the present in vivo pigs study to investigate quality, safety, and efficacy of SBO’s as animal feed supplement. Total 106 male and female piglets were fed 42 days with protein-based diets containing 0.1 and 0.2 % SBO. Pigs grew from average 7.7 to 26 kg. Average mortality rate was 3.9 %. Relatively to control diets with no added SBO, the diets containing 0.1 and 0.2 % SBO evidenced no significant effects on pigs’ growth, mortality, and anatomy and pathology of dead animals. A previous rabbit study reported similar results for SBO supplemented diets. The authors discuss the economic and environmental implications of the results in relation to SBO potential marketability

Multi-instrument observations of a failed flare eruption associated with MHD waves in a loop bundle

Context. We present observations of a B7.9 class flare that occurred on January 24th, 2015, using SDO/AIA, Hinode/EIS and XRT. The flare triggers an eruption of a dense cool plasma blob as seen in AIA 171Å which is unable to completely break out and remains confined within a local bundle of active region loops. During this process, transverse oscillations of the threads are observed. The cool plasma is then observed to descend back to the chromosphere along each loop strand. At the same time, a larger diffuse co-spatial loop observed in the hot wavebands of SDO/AIA and Hinode/XRT is formed, exhibiting periodic intensity variations along its lenght. Aims. The formation and evolution of magnetohydrodynamic (MHD) waves depend upon the values of the local plasma parameters (e.g., density, temperature, magnetic field) which can hence be inferred by coronal seismology. In this study we aim to assess how the observed MHD modes are affected by the variation of density and temperature. Methods. We combine analysis of EUV/X-ray imaging and spectroscopy using SDO/AIA, Hinode/EIS and XRT. Results. The transverse oscillations of the cool loop threads are interpreted in terms of vertically polarised kink oscillations. The fitting procedure provides estimates for the period of about 3.5–4 min, and the amplitude of ∼ 5 Mm. The oscillations are strongly damped showing very low quality factor (1.5–2), which is defined as the ratio of the damping time and the oscillation period. The weak variation of the period of the kink wave, which is estimated from the fitting analysis, is in agreement with the density variations due to the presence of the plasma blob inferred from the intensity light curve at 171Å. The coexisting intensity oscillations along the hot loop are interpreted as a slow MHD wave with the period of 10 min and phase speed of about 436 km s−1 . Comparison between the fast and slow modes allows for the determination of the Alfvén speed, and consequently magnetic field values. The plasma-β inferred from the analysis is estimated to be around 0.1–0.3. Conclusions. We show that the evolution of the detected waves is determined by the temporal variations of the local plasma parameters, caused by the flare heating and the consequent cooling. We apply coronal seismology to both waves obtaining estimations of the background plasma parameter

Bell inequalities as constraints on unmeasurable correlations

The interpretation of the violation of Bell-Clauser-Horne inequalities is revisited, in relation with the notion of extension of QM predictions to unmeasurable correlations. Such extensions are compatible with QM predictions in many cases, in particular for observables with compatibility relations described by tree graphs. This implies classical representability of any set of correlations , , , and the equivalence of the Bell-Clauser-Horne inequalities to a non void intersection between the ranges of values for the unmeasurable correlation associated to different choices for B. The same analysis applies to the Hardy model and to the "perfect correlations" discussed by Greenberger, Horne, Shimony and Zeilinger. In all the cases, the dependence of an unmeasurable correlation on a set of variables allowing for a classical representation is the only basis for arguments about violations of locality and causality.Comment: Some modifications have been done in order to improve clarity of presentation and comparison with other approache

Dissolved organic carbon retention by coprecipitation during the oxidation of ferrous iron (EGU2018-3906)

Although the importance of Fe (hydr)oxides for soil organic matter (OM) stabilization and C retention by surface adsorption is well known, only recently has coprecipitation been recognized as an important process responsible for C storage in hydromorphic soils, such as rice paddy soils. Under periodic fluctuations in redox conditions the interaction between dissolved organic carbon (DOC) and Fe (hydr)oxides may not only involve organic coatings on mineral surfaces, but also Fe-DOC coprecipitates that form during the oxidation of soil solutions containing important amounts of DOC and Fe2+. The aim of this work was to provide new insights into the mechanisms involved, and the amount and selectivity of C retained during the coprecipitation process. A series of Fe-OM associations with increasing C loading was synthesized at pH 6 by surface adsorption or coprecipitation (oxidation of ferrous iron) utilizing rice-straw derived dissolved organic matter. The kinetics of Fe2+ oxidation and complexation, and the total and selective retention of DOC during the coprecipitation process were evaluated. Moreover, synthesized associations, as well as a field coprecipitate collected in situ from a paddy soil, were studied by X-ray diffraction, N2 gas adsorption-desorption isotherms, electrophoretic mobility measurements and thermogravimetric analyses. Coprecipitation resulted in higher organic C contents (49-213 mg g-1) with respect to adsorbed systems (18-47 mg g-1), and favoured the inclusion of OM within highly aggregated associations having particularly low BET specific surface areas. Coprecipitates sampled in situ also showed a similar retention of organic C confirming that this process may contribute significantly to the OM stabilization in paddy topsoils. The mechanisms involved in the retention of straw-derived DOM during coprecipitation were shown to be strongly dependent on C/Fe ratio of the solution. Although the overall coprecipitation process was highly selective for aromatic constituents, initial complexation of Fe2+ and precipitation as C-rich metal salts involved the selective interaction with aliphatic carboxylic constituents. The contribution of the latter mechanism to total C retention during coprecipitation was shown to increase with increasing solution C/Fe ratios. These aliphatic complexes formed during coprecipitation may play an important, though often underestimated, role in C stabilization in hydromorphic. The process-related selectivity of specific constituents of DOM during coprecipitation highlights the involvement of specific mechanisms, i.e. complexation, adsorption, salt precipitation, while ruling out non-selective, physical occlusion of OM within the forming coprecipitat

Observing the corona and inner heliosphere with Parker Solar Probe

The recently launched Parker Solar Probe (PSP) mission is expected to provide unprecedented views of the solar corona and inner heliosphere. In addition to instruments devoted to taking measurements of the local solar wind, the spacecraft carries a visible imager: the Wide-field Imager for Solar PRobe (WISPR). WISPR will take advantage of the proximity of the spacecraft to the Sun to perform local imaging of the near-Sun environment. WISPR will observe coronal structures at high spatial and time resolutions, although the observed plane-of-sky will rapidly change because of the fast transit at the perihelia. We present a concise description of the PSP mission, with particular regard to the WISPR instrument, discussing its main scientific goals, targets of observations, and outlining the possible synergies with current and upcoming space missions

Inflammation subverts hippocampal synaptic plasticity in experimental multiple sclerosis

Abnormal use-dependent synaptic plasticity is universally accepted as the main physiological correlate of memory deficits in neurodegenerative disorders. It is unclear whether synaptic plasticity deficits take place during neuroinflammatory diseases, such as multiple sclerosis (MS) and its mouse model, experimental autoimmune encephalomyelitis (EAE). In EAE mice, we found significant alterations of synaptic plasticity rules in the hippocampus. When compared to control mice, in fact, hippocampal long-term potentiation (LTP) induction was favored over long-term depression (LTD) in EAE, as shown by a significant rightward shift in the frequency-synaptic response function. Notably, LTP induction was also enhanced in hippocampal slices from control mice following interleukin-1β (IL-1β) perfusion, and both EAE and IL-1β inhibited GABAergic spontaneous inhibitory postsynaptic currents (sIPSC) without affecting glutamatergic transmission and AMPA/NMDA ratio. EAE was also associated with selective loss of GABAergic interneurons and with reduced gamma-frequency oscillations in the CA1 region of the hippocampus. Finally, we provided evidence that microglial activation in the EAE hippocampus was associated with IL-1β expression, and hippocampal slices from control mice incubated with activated microglia displayed alterations of GABAergic transmission similar to those seen in EAE brains, through a mechanism dependent on enhanced IL-1β signaling. These data may yield novel insights into the basis of cognitive deficits in EAE and possibly of MS