•2-butyl-hexahydropyrrolo1,2-b1,2oxazole was used as a MS corrosion inhibitor in 0.5M HCl.•DC, EIS and gravimetric measurements were performed in the 30–60°C temperature range.•After 48h, the ...inhibitor is inefficient below 30°C; in the 40–60°C the ηWL reached a >95% at 40°C.•In acid, the synergistic effect of Cl− with BPOX was demonstrated by UV and PZC methods.
The use of 2-butyl-hexahydropyrrolo1,2-b1,2oxazole (BPOX) as a corrosion inhibitor of mild steel (MS) – with a polished or a pre-corroded (for 2h) surface – was tested in 0.5M aerated hydrochloric acid in the 30–60°C temperature range. Its inhibition effectiveness (IE) was assessed after short (2h) and longer (48h) immersion time tests, through potentiodynamic, EIS and weight loss (WL) measurements. At low immersion times (2h) the potentiodynamic tests indicated that BPOX inhibited corrosion reaction of the polished MS surface at all temperatures, acting as a mixed-type inhibitor and reaching, in many experimental conditions, inhibitor efficiency values ηp>95%. This behavior was confirmed by the EIS results, with the exception of those obtained at 40°C, where the ηEIS did not decrease dramatically, ranging between 55% and 81%. These results were not confirmed by the WL experiments carried out on pre-corroded MS specimens at longer immersion time (48h): BPOX did not act as an inhibitor until 30°C, and in the 40–60°C the ηWL reached a maximum at 40°C and 5×10−3M (ηWL>95%), then decreasing but not so dramatically until 60°C. Starting from these results, it was demonstrated that after 48h the adsorption mechanism visibly changed between 30 and 40°C. Moreover, 40°C is the optimum temperature for the inhibitive BPOX action by means of potentiodynamic test carried out after 48h. The MS potential of zero charge (EZC) in 5×10−3M BPOX at 40°C was found to be −530mVSCE: it was demonstrated that the presence of Cl− in acidic medium promoted the BPOX corrosion inhibition of the positively charged MS surface. Potentiodynamic experiments carried out in the 10−3M BPOX presence (40°C) showed that ηp value obtained in 0.5M HCl (ηp=94% after 24h) was even passed in 0.5M H2SO4+0.5M NaCl (ηp=>95%). The negative ΔGads° values calculated (approximately −30 to −34kJ/mol), lower than −20kJ/mol but not as low as −40kJ/mol, indicated the stability of the adsorbed layer and that the BPOX adsorption mechanism was more than a physisorption, but not a true chemisorption.
The experimental test of novel ultrasound (US) investigation methods can be made difficult by the lack of flexibility of commercial US machines. In the best options, these only provide beamformed ...radiofrequency or demodulated echo-signals for acquisition by an external PC. More flexibility is achieved in high-level research platforms, but these are typically characterized by high cost and large size. This paper presents a powerful but portable US system, specifically developed for research purposes. The system design has been based on high-level commercial integrated circuits to obtain the maximum flexibility and wide data access with minimum of electronics. Preliminary applications involving nonstandard imaging transmit/receive strategies and simultaneous B-mode and multigate spectral Doppler mode are discussed.
We have observed the Andromeda galaxy, Messier 31 (M31), at 6.7 GHz with the Sardinia Radio Telescope. We mapped the radio emission in the C-band, re-analyzed WMAP and Planck maps, as well as other ...ancillary data, and we have derived an overall integrated flux density spectrum from the radio to the infrared. This allowed us to estimate the emission budget from M31. Integrating over the whole galaxy, we found strong and highly significant evidence for anomalous microwave emission (AME), at the level of Jy at the peaking frequency of 25 GHz. Decomposing the spectrum into known emission mechanisms such as free-free, synchrotron, thermal dust, and AME arising from electric dipole emission from rapidly rotating dust grains, we found that the overall emission from M31 is dominated, at frequencies below 10 GHz, by synchrotron emission with a spectral index of , with subdominant free-free emission. At frequencies 10 GHz, AME has a similar intensity to that of synchrotron and free-free emission, overtaking them between 20 and 50 GHz, whereas thermal dust emission dominates the emission budget at frequencies above 60 GHz, as expected.
The inhibition effects of tryptamine (TA) on the corrosion behaviour of ARMCO iron in 0.5 M deaerated H
2SO
4 (in the 25–55 °C temperature range) was studied in both short and long time tests (1, 24 ...and 72 h) by means of potentiodynamic curves (PCM) and electrochemical impedance spectroscopy (EIS). TA was found to be an effective ARMCO iron inhibitor, even at 55 °C and 72 h, but only at 10 mM. At this concentration the inhibition percentages (IP%), calculated by PCM and EIS, ranged from 90% to 99% and did not diminish over time and as the temperature increased. TA adsorption followed Bockris–Swinkels’ isotherm (
x=1). The thermodynamic data indicated that, in the more concentrated solutions, TA also chemisorbed on the iron surface.
The use of Tryptophan (Trp) as a copper corrosion inhibitor was tested in 0.5 M aerated sulfuric acid (H
2SO
4) in the 20–
50
°
C
temperature range. Its effectiveness was assessed through ...potentiodynamic (at 1 h, 72 h, 6 months), spectrophotometric (72 h tests) and gravimetric (72 h tests) tests. At 20–
50
°
C
(1 h tests) the Trp adsorption followed Bockris–Swinkels' isotherm (
x=2). The Trp even underwent over time (six month) a photodegradation, but surprisingly enough this did not affect the inhibition percentage (IP) which was 80% for the solutions kept in the dark as well as those kept in light.
ABSTRACT
Map-making is an important step for the data analysis of cosmic microwave background (CMB) experiments. It consists of converting the data, which are typically a long, complex, and noisy ...collection of measurements, into a map, which is an image of the observed sky. We present in this paper a new map-making code named picasso (Polarization and Intensity CArtographer for Scanned Sky Observations), which was implemented to construct intensity and polarization maps from the Multi Frequency Instrument (MFI) of the QUIJOTE (Q-U-I Joint TEnerife) CMB polarization experiment. picasso is based on the destriping algorithm, and is suited to address specific issues of ground-based microwave observations, with a technique that allows the fit of a template function in the time domain, during the map-making step. This paper describes the picasso code, validating it with simulations and assessing its performance. For this purpose, we produced realistic simulations of the QUIJOTE-MFI survey of the northern sky (approximately ∼20 000 deg2), and analysed the reconstructed maps with picasso, using real and harmonic space statistics. We show that, for this sky area, picasso is able to reconstruct, with high fidelity, the injected signal, recovering all the scales with ℓ > 10 in TT, EE, and BB. The signal error is better than 0.001 per cent at 20 < ℓ < 200. Finally, we validated some of the methods that will be applied to the real wide-survey data, like the detection of the CMB anisotropies via cross-correlation analyses. Despite that the implementation of picasso is specific for QUIJOTE-MFI data, it could be adapted to other experiments.
ABSTRACT
Anomalous Microwave Emission (AME) is a significant component of Galactic diffuse emission in the frequency range 10–$60\, \mathrm{GHz}$ and a new window into the properties of ...sub-nanometre-sized grains in the interstellar medium. We investigate the morphology of AME in the ≈10○ diameter λ Orionis ring by combining intensity data from the QUIJOTE experiment at 11, 13, 17, and $19\, \mathrm{GHz}$ and the C-Band All Sky Survey (C-BASS) at $4.76\, \mathrm{GHz}$, together with 19 ancillary data sets between 1.42 and $3000\, \mathrm{GHz}$. Maps of physical parameters at 1○ resolution are produced through Markov chain Monte Carlo (MCMC) fits of spectral energy distributions (SEDs), approximating the AME component with a lognormal distribution. AME is detected in excess of $20\, \sigma$ at degree-scales around the entirety of the ring along photodissociation regions (PDRs), with three primary bright regions containing dark clouds. A radial decrease is observed in the AME peak frequency from $\approx 35\, \mathrm{GHz}$ near the free–free region to $\approx 21\, \mathrm{GHz}$ in the outer regions of the ring, which is the first detection of AME spectral variations across a single region. A strong correlation between AME peak frequency, emission measure and dust temperature is an indication for the dependence of the AME peak frequency on the local radiation field. The AME amplitude normalized by the optical depth is also strongly correlated with the radiation field, giving an overall picture consistent with spinning dust where the local radiation field plays a key role.
ABSTRACT
Anomalous microwave emission (AME) is an important emission component between 10 and 60 GHz that is not yet fully understood. It seems to be ubiquitous in our Galaxy and is observed at a ...broad range of angular scales. Here we use the new QUIJOTE-MFI wide survey data at 11, 13, 17, and 19 GHz to constrain the AME in the Galactic plane (|b| < 10°) on degree scales. We built the spectral energy distribution between 0.408 and 3000 GHz for each of the 5309 0.9° pixels in the Galactic plane, and fitted a parametric model by considering five emission components: synchrotron, free–free, AME, thermal dust and CMB anisotropies. We show that not including QUIJOTE-MFI data points leads to the underestimation (up to 50 per cent) of the AME signal in favour of free–free emission. The parameters describing these components are then intercompared, looking for relations that help to understand AME physical processes. We find median values for the AME width, WAME, and for its peak frequency, νAME, respectively of $0.560^{+0.059}_{-0.050}$ and $20.7^{+2.0}_{-1.9}$ GHz, slightly in tension with current theoretical models. We find spatial variations throughout the Galactic plane for νAME, but only with reduced statistical significance. We report correlations of AME parameters with certain ISM properties, such as that between the AME emissivity (which shows variations with the Galactic longitude) and the interstellar radiation field, and that between the AME peak frequency and dust temperature. Finally, we discuss the implications of our results on the possible molecules responsible for AME.
ABSTRACT
We derive linearly polarized astrophysical component maps in the Northern Sky from the QUIJOTE-MFI data at 11 and 13 GHz in combination with the Wilkinson Microwave Anisotropy Probe K and Ka ...bands (23 and 33 GHz) and all Planck polarized channels (30–353 GHz), using the parametric component separation method B-SeCRET. The addition of QUIJOTE-MFI data significantly improves the parameter estimation of the low-frequency foregrounds, especially the estimation of the synchrotron spectral index, βs. We present the first detailed βs map of the Northern Celestial Hemisphere at a smoothing scale of 2°. We find statistically significant spatial variability across the sky. We obtain an average value of −3.08 and a dispersion of 0.13, considering only pixels with reliable goodness of fit. The power-law model of the synchrotron emission provides a good fit to the data outside the Galactic plane but fails to track the complexity within this region. Moreover, when we assume a synchrotron model with uniform curvature, cs, we find a value of cs = −0.0797 ± 0.0012. However, there is insufficient statistical significance to determine which model is favoured, either the power law or the power law with uniform curvature. Furthermore, we estimate the thermal dust spectral parameters in polarization. Our cosmic microwave background, synchrotron, and thermal dust maps are highly correlated with the corresponding products of the PR4 Planck release, although some large-scale differences are observed in the synchrotron emission. Finally, we find that the βs estimation in the high signal-to-noise synchrotron emission areas is prior-independent, while, outside these regions, the prior governs the βs estimation.
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