Coherent curvature radiation and Fast Radio Bursts

Fast radio bursts are extragalactic radio transient events lasting a few milliseconds with a ~Jy flux at ~1 GHz. We propose that these properties suggest a neutron star progenitor, and focus on coherent curvature radiation as the radiation mechanism. We study for which sets of parameters the emission can fulfil the observational constraints. Even if the emission is coherent, we find that self-absorption can limit the produced luminosities at low radio frequencies and that an efficient re-acceleration process is needed to balance the dramatic energy losses of the emitting particles. Self-absorption limits the luminosities at low radio frequency, while coherence favours steep optically thin spectra. Furthermore, the magnetic geometry must have a high degree of order to obtain coherent curvature emission. Particles emit photons along their velocity vectors, thereby greatly reducing the inverse Compton mechanism. In this case we predict that fast radio bursts emit most of their luminosities in the radio band and have no strong counterpart in any other frequency bands.Comment: 8 pages, 3 figures, 1 table. Accepted for publication in A&

The challenge of detecting intracluster filaments with Faraday Rotation

The detection of filaments in the cosmic web will be crucial to distinguish between the possible magnetogenesis scenarios and future large polarization surveys will be able to shed light on their magnetization level. In this work, we use numerical simulations of galaxy clusters to investigate their possible detection. We compute the Faraday Rotation signal in intracluster filaments and compare it to its surrounding environment. We find that the expected big improvement in sensitivity with the SKA-MID will in principle allow the detection of a large fraction of filaments surrounding galaxy clusters. However, the contamination of the intrinsic Faraday Rotation of background polarized sources will represent a big limiter to the number of objects that can be significantly detected. We discuss possible strategies to minimize this effect and increase the chances of detection of the cosmic web with the large statistics expected from future surveys.Comment: 16 pages, accepted to Galaxie

The luminosity--volume test for cosmological Fast Radio Bursts

We perform the luminosity--volume test, also known as $\langle V/V_{MAX}\rangle$, to Fast Radio Bursts (FRBs). We compare the 23 FRBs, recently discovered by ASKAP, with 20 of the FRBs found by Parkes. These samples have different flux limits and correspond to different explored volumes. We assume that their dispersion measure indicates their redshift and apply the appropriate cosmological corrections to the spectrum and rate in order to compute the $\langle V/V_{MAX}\rangle$ for the ASKAP and Parkes samples. For a radio spectrum of FRBs $F_\nu \propto \nu^{-1.6}$, we find $\langle V/V_{MAX}\rangle=0.66\pm 0.05$ for the ASKAP sample, that includes FRBs up to $z=0.7$, and 0.52$\pm 0.04$ for Parkes, that extends up to $z=2.1$. The ASKAP value suggests that the population of FRB progenitors evolves faster than the star formation rate, while the Parkes value is consistent with it. Even a delayed (as a power law or gaussian) star formation rate cannot reproduce the $\langle V/V_{MAX}\rangle$ of both samples. If FRBs do not evolve in luminosity, the $\langle V/V_{MAX}\rangle$ values of ASKAP and Parkes sample are consistent with a population of progenitors whose density strongly evolves with redshift as $\sim z^{2.8}$ up to $z \sim 0.7$. We discuss possible scenarios accounting for our results.Comment: 10 pages, 5 figures, 3 tables, accepted by A&A on 2019/04/0

On detecting the cosmic web and its magnetic field

Magnetic fields are known to permeate space over a remarkable range of scales, from meter-large bodies up to ~Mpc wide clusters of galaxies. It is still debated whether their origin is either "primordial", involving their early formation in the homogeneous universe, or "astrophysical", i.e. from feedback into the inter-galactic space by the first dense and highly magnetised structures (e.g. stars, galaxies, AGN). Observing galaxy cluster outskirts and filaments of the cosmic web is keys to test the above scenarios, as the current strength and morphology of their evolved magnetic field should correlate with the initial conditions in the most rarefied environments. In this thesis, we push complementary radio-astronomy techniques (namely direct imaging, Faraday rotation and FRB studies) on dedicated data from new generation instruments, in combination with state-of-the-art cosmological simulations, to constrain the properties of the magnetic fields at ~Mpc scale at low redshift. This work provides relevant advances into observational constraints of magnetic fields in cluster outskirts (e.g. 0.4uG<B_Mpc<10uG in the outskirts of the galaxy cluster A2249) and intra-cluster filaments (B_Mpc<0.25-0.75uG). We explore the feasibility and possible systematics of Faraday rotation studies with new and next generation instrumentation (JVLA, SKA) and provide new perspectives to best exploit their use. We also constrain the population properties of fast radio bursts (FRBs), which can be used as background sources for the study of the large scale structures. Our findings hint to either an evolving luminosity function of FRBs or to the presence of un-diagnosed selection effect in the current avaliable samples. Finally, we plan (and implement) the refurbishment of an old radio telescope, the Northern Cross in Medicina, for dedicated FRB search. We characterise the instrument sensitivity at 408 MHz and estimate detection rates with respect to different complementary set-up, e.g. a follow-up mode of known FRBs and a wide-area survey

Chemical composition and phytosterols profile of degermed maize products derived from wet and dry milling

Maize is part of the diet of populations of all socio-economic classes in many countries around the world and is an excellent source of bioactive compounds such as carotenoids, phytosterols and lignans. Phytosterols have gained considerable interest because they possess properties that significantly reduce cholesterol levels in the blood by acting as antagonists. The purpose of this study was to characterise the fractions of maize flour obtained from Italian wet and dry milling processes from a chemical viewpoint (crude proteins, crude lipids and starch) and the contents of three main phytosterols. Whole parameters exhibited a broad variability in their content. The crude protein, crude lipids and starch contents ranged from 7.43 to 18.38% dry matter (dm), 0.61 to 8.53% dm and 23.77 to 80.41% dm, respectively, and the total phytosterol content ranged from 4.6 to 53.48 mg 100 g-1 dm. Significant differences were observed in the phytosterol compositions measured in degermed maize products obtained from wet and dry milling. The campesterol content ranged from 0.54 to 6.19 mg 100 g-1 dry weight (dw), respectively, for maize flour III and dry milling maize meal feed. The stigmasterol content ranged from 0.55 to 4.77 mg 100 g-1 dw for hominy grits II and broken degermed type I, respectively. In addition, the β-sitosterol content varied significantly from 2.51 to 44.37 mg 100 g-1 dw for hominy grits II and dry milling maize meal feed, respectively

Graminex pollen: phenolic pattern, colorimetric analysis and protective effects in immortalized prostate cells (PC3) and rat prostate challenged with LPS

Prostatitis, a general term describing prostate inflammation, is a common disease that could be sustained by bacterial or non-bacterial infectious agents. The efficacy of herbal extracts with antioxidant and anti-inflammatory effects for blunting the burden of inflammation and oxidative stress, with possible improvements in clinical symptoms, is under investigation. Pollen extracts have been previously reported as promising agents in managing clinical symptoms related to prostatitis. The aim of the present work was to evaluate the protective effects of Graminex pollen (GraminexTM, Deshler, OH, USA), a commercially available product based on standardized pollen extracts, in rat prostate specimens, ex vivo. In this context, we studied the putative mechanism of action of pollen on multiple inflammatory pathways, including the reduction of prostaglandin E2 (PGE2), nuclear factor kappa-light-chain-enhancer of activated B cells (NFB), and malondialdehyde (MDA), whose activities were significantly increased by inflammatory stimuli. We characterized by means of chromatographic and colorimetric studies the composition of Graminex pollen to better correlate the activity of pollen on immortalized prostate cells (PC3), and in rat prostate specimens challenged with Escherichia coli lipopolysaccharide (LPS). We found that Graminex pollen was able to reduce radical oxygen species (ROS) production by PC3 cells and MDA, NFB mRNA, and PGE2 levels, in rat prostate specimens. According to our experimental evidence, Graminex pollen appears to be a promising natural product for the management of the inflammatory components in the prostate