Context.
Supernova remnants interacting with molecular clouds are ideal laboratories to study the acceleration of particles at shock waves and their transport and interactions in the surrounding ...interstellar medium.
Aims.
Here, we focus on the supernova remnant W28, which over the years has been observed in all energy domains from radio waves to very-high-energy gamma rays. The bright gamma-ray emission detected from molecular clouds located in its vicinity revealed the presence of accelerated GeV and TeV particles in the region. An enhanced ionization rate has also been measured by means of millimeter observations, but such observations alone cannot tell us whether the enhancement is due to low-energy (MeV) cosmic rays (either protons or electrons) or the X-ray photons emitted by the shocked gas. The goal of this study is to determine the origin of the enhanced ionization rate and to infer from multiwavelength observations the spectrum of cosmic rays accelerated at the supernova remnant shock in an unprecedented range spanning from MeV to multi-TeV particle energies.
Methods.
We developed a model to describe the transport of X-ray photons into the molecular cloud, and we fitted the radio, millimeter, and gamma-ray data to derive the spectrum of the radiating particles.
Results.
The contribution from X-ray photons to the enhanced ionization rate is negligible, and therefore the ionization must be due to cosmic rays. Even though we cannot exclude a contribution to the ionization rate coming from cosmic-ray electrons, we show that a scenario where cosmic-ray protons explain both the gamma-ray flux and the enhanced ionization rate provides the most natural fit to multiwavelength data. This strongly suggests that the intensity of CR protons is enhanced in the region for particle energies in a very broad range covering almost six orders of magnitude: from ≲100 MeV up to several tens of TeV.
New high surface area nano-architectured copper current collectors have been designed based on simple electrodeposition method. The nano-architectured electrode design not only increases the ...effective surface area of the electrode but it is also very suitable for sustaining the mechanical and structural strain during electrochemical reaction. In this work, a nano-architectured Sn anode for Li-ion battery, based on Li–Sn alloying reaction, delivers very high cycle life and good power performance compared to planar tin films. This electrode could be successfully used in the field of 3D microbatteries.
The anticorrosion performances of a system consisting of a phosphate based conversion layer and a hybrid sol–gel coating have been evaluated for the magnesium alloy Elektron21. The lone sol–gel ...coating affords a significant protection of the magnesium substrate. However, the presence of an intermediate conversion layer is presumed to improve the corrosion resistance of the system. The surface morphology of the protection coatings was characterized by optical microscopy, scanning electron microscopy (SEM) and white-light source interferometry. The corrosion behavior of the systems was analyzed by electrochemical impedance spectroscopy (EIS). The impedance measurements show that the presence of the added conversion layer increases the resistance of the whole system during immersion in a 0.05M NaCl solution, compared to the single sol–gel coating.
•A hybrid sol–gel film was tested for corrosion protection of magnesium.•A phosphate conversion layer was produced on the magnesium.•The hybrid sol–gel film and the conversion layer were tested in combination.•The corrosion resistance increases with the thickness of the conversion layer.
An Eighteenth Dynasty Egyptian sealed pottery stored at the Museum of Aquitaine (Bordeaux, France) has been investigated using terahertz radiation, X-rays and neutrons. THz computed tomography ...revealed nondestructively the presence of content, whereas X-rays and neutrons analyzed more precisely the fabrication process and conservation of the pottery together with the nature of this content owing to higher spatial resolution and contrast. With neutron tomography, we determined the method used to seal the jar as well as the finer structure of the inner content. Neutron-induced prompt gamma spectroscopy was finally applied to measure the elemental composition of the content, which is supposed to consist of dried germinated seeds.
Luminescent silica nanoparticles are frequently employed for biotechnology applications mainly because of their easy functionalization, photo-stability, and biocompatibility. Bifunctional silica ...nanoparticles (BSNPs) are described here as new efficient tools for investigating complex biological systems such as biofilms. Photoluminescence is brought about by the incorporation of a silylated ruthenium(II) complex. The surface properties of the silica particles were designed by reaction with amino-organosilanes, quaternary ammonium-organosilanes, carboxylate-organosilanes and hexamethyldisilazane. BSNPs were characterized extensively by DRIFT,
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Si solid state NMR, XPS, and photoluminescence. Zeta potential and contact angle measurements exhibited various surface properties (hydrophilic/hydrophobic balance and electric charge) according to the functional groups. Confocal laser scanning microscopy (CLSM) measurements showed that the spatial distribution of these nanoparticles inside a biofilm of Pseudomonas aeruginosa PAO1 depends more on their hydrophilic/hydrophobic characteristics than on their size. CLSM observations using two nanosized particles (25 and 68 nm) suggest that narrow diffusion paths exist through the extracellular polymeric substances matrix.
To study degradation processes occurring on painting materials, the use of high-resolution micro-analytical techniques is highly requested since it provides a detailed identification and localisation ...of both the original and deteriorated ingredients. Among the various pigments recently studied, the characterisation of verdigris has received a major interest. This pigment has not a unique chemical formula, but its composition depends on the recipe employed for its manufacturing. Moreover, verdigris paints are not stable and are subject to a colour change from blue-green to green, which occurs in the first few months after the application. In this paper, we focused our attention on the use of ATR-FTIR mapping as a useful method to identify verdigris secondary products and pathways. Several mock-ups and real samples have been analysed, and the correlation among the detected compounds and their spatial location, obtained by the application of ATR-FTIR microscopy in mapping mode, allowed formulating some hypotheses on the degradation pattern of verdigris, which may feed the discussion on the transformation and stability of this pigment. From an analytical point of view, we showed how FTIR mapping approaches may be extremely useful both for the identification of compounds in complex matrix in which single spectra may limit the exhaustive characterisations due to bands overlapping and for the study of degradation pathways by taking into consideration the relative distribution of degradation products.
Terahertz time domain spectroscopic imaging (THz-TDSI) is a non-ionizing, non-contact and non-destructive measurement technique that has been recently utilized to study cultural heritage artifacts. ...We will present this technique and the results of non-contact measurements of papyrus texts, including images of hidden papyri. Inks for modern papyrus specimens were prepared using the historical binder, Arabic gum, and two common pigments used to write ancient texts, carbon black and red ochre. The samples were scanned in reflection at normal incidence with a pulse with a spectral range between 0.1 and 1.5 THz. Temporal analysis of the signals provides the depths of the layers, and their frequency spectra give information about the inks.
South African rock art provides a window into the Bushman worldview. For a better understanding of Bushman history and beliefs and the conservation of rock art sites, a better knowledge of the ...materials making up the paints, the mineral accretions and their alterations is required. A conjunction of imaging techniques (optical microscopy, SEM–EDX, Raman spectromicroscopy and synchrotron FT–IR) allowed us to describe the complex layered fabric that evidences a history of accretion, painting and alteration in eight samples of painted rock. Two types of paints are identified and the distribution of calcium oxalates is discussed in terms of conservation and dating potential.
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