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A global climatology of sporadic-E occurrence rates (ORs) based on ionosonde measurements is presented for the peak blanketing frequency, fbEs, and the ordinary mode peak frequency of the layer, foEs. ORs are calculated for a variety of sporadic-E frequency thresholds: no lower limit, 3, 5, and 7 MHz. Seasonal rates are calculated from 64 Digisonde sites during the period 2006–2020 using ionograms either manually or automatically scaled with ARTIST-5. Both foEs and fbEs ORs peak in the Northern Hemisphere during the boreal summer, with a decrease by roughly a factor of 2–3 in fbEs rates relative to foEs rates without a lower threshold on the sporadic-E intensity. This ratio of foEs to fbEs OR increases with increasing sporadic-E intensity, up to a factor of 5 for the 7 MHz threshold. An asymmetry is observed with the Southern Hemisphere peaks during the austral summer, with slightly lower rates compared with the Northern Hemisphere during the boreal summer. A drastic decrease in ORs is observed for the higher intensity thresholds, such that the fbEs occurrence rates for 7 MHz are nearly zero during most locations and seasons. These updated occurrence rates can be used for future statistical comparisons with GPS radio occultation-based sporadic-E occurrence rates.

Single-column sea ice models are used to focus on the thermodynamic evolution of the ice. Generally these models are forced by atmospheric reanalysis in absence of atmospheric in situ observations. Here we assess the sea ice thickness (SIT) simulated by a single-column model (ICEPACK) with in situ observations obtained off Zhongshan Station for the austral winter of 2016. In the reanalysis the surface air temperature is about 1 °C lower, the total precipitation is about 2 mm day−1 larger, and the surface wind speed is about 2 m s−1 higher compared to the in situ observations, respectively. Using sensitivity experiments we evaluate the simulation bias in sea ice thickness due to the uncertainty in the individual atmospheric forcing variables. We show that the unrealistic precipitation in the reanalysis leads to a bias of 14.5 cm in sea ice thickness and of 17.3 cm in snow depth. In addition, our data show that increasing snow depth works to gradually inhibits the growth of sea ice associated with thermal blanketing by the snow due to changing the vertical heat flux. Conversely, given suitable conditions, the sea ice thickness may grow suddenly when the snow load gives rise to flooding and leads to snow-ice formation. A potential mechanism to explain the different characteristics of the precipitation bias on snow and sea ice is discussed. The flooding process for landfast sea ice might cause different effect compared to pack ice, thus need to be reconsidered in ICEPACK. Meanwhile, the overestimation in surface wind speed in reanalysis is likely responsible for the underestimation in simulated snow depth, however this had little influence on the modelled ice thickness.

In this study we present the behaviour of sporadic E-layer during a total solar eclipse (TSE) which occurred during the dawn/sunrise hours over a site located in the path of totality. A Canadian Advanced Digital Ionosonde (CADI) was operated at Allahabad (25.4° N, 81.9° E), a low latitude station located near the crest of equatorial ionization anomaly (EIA) in the Indian subcontinent to study the ionospheric effects of 22 July 2009 TSE. Corresponding to the eclipse period, a gradual increase of ftEs (top frequency of Es layer) in the 4–5 MHz range was seen on the control days. On 22 July (the TSE day), correlated changes in ftEs coinciding with the TSE progression was noted – (i) sharp decrease near first and second contact of TSE, (ii) an increase after first and second contact, and (iii) wavelike fluctuations in ftEs variation during eclipse hours and beyond. Much higher ftEs values were noted during the TSE hours in comparison to that seen on usual days. Strong blanketing Es layer developed during the TSE hours and persisted for slightly longer duration than its usual occurrence time. Near the TSE totality, slight lowering of the base height of Es layer was also noted.

Line-driven wind instability is expected to cause small-scale wind inhomogeneities, X-ray emission, and wind line profile variability. The instability can already develop around the sonic point if it is initiated close to the photosphere due to stochastic turbulent motions. In such cases, it may leave its imprint on the light curve as a result of wind blanketing. We study the photometric signatures of the line-driven wind instability. We used line-driven wind instability simulations to determine the wind variability close to the star. We applied two types of boundary perturbations: a sinusoidal one that enables us to study in detail the development of the instability and a stochastic one given by a Langevin process that provides a more realistic boundary perturbation. We estimated the photometric variability from the resulting mass-flux variations. The variability was simulated assuming that the wind consists of a large number of independent conical wind sectors. We compared the simulated light curves with TESS light curves of OB stars that show stochastic variability. We find two typical signatures of line-driven wind instability in photometric data: a knee in the power spectrum of magnitude fluctuations, which appears due to engulfment of small-scale structure by larger structures, and a negative skewness of the distribution of fluctuations, which is the result of spatial dominance of rarefied regions. These features endure even when combining the light curves from independent wind sectors. The stochastic photometric variability of OB stars bears certain signatures of the line-driven wind instability. The distribution function of observed photometric data shows negative skewness and the power spectra of a fraction of light curves exhibit a knee. This can be explained as a result of the line-driven wind instability triggered by stochastic base perturbations., 9 pages, accepted for publication in Astronomy & Astrophysics

Transferring wine is a common operation in most of the wineries in the world that depends mainly on the equipment and materials used. These contributions are widely unknown, and their knowledge is of vital importance to controlling the winemaking process. This work presents the results of characterizing the oxygen supply due to the use of hoses of different materials (Butyl Rubber, IIR, Nitrile Butadiene Rubber, NBR, Ethylene Propylene Diene Monomer rubber, EPDM, Ultra-high-molecular-weight polyethylene, UHMW, Natural Rubber, NR), dimensions (DN32, DN50), connectors (DIN 11851, Tri-CLAMP) with gaskets of different materials (NBR, EPDM, Fluorocarbon, FKM/FPM, silicone rubber, Q/VMQ, Polytetrafluoroethylene, PTFE). In addition, the use of different inert gases (N2, CO2, Ar, N2 + CO2 and Ar + CO2) for air purging of hoses and tanks, as well as for ullage blanketing during tank-to-tank racking, and their economic impact were studied. The results indicated that the IIR hoses had the least amount of O2 added to the liquid and that the Tri-clamp connectors were generally more airtight, with the FKM seals standing out. The most recommended inert gas was CO2 when the type of wine allows it, N2 being the most recommended in any case. When all these recommendations were used together the addition of O2 during tank-to-tank racking was drastically reduced.

The conventional use of ‘globally averaged temperatures’ causes ambiguity in our perception of human climate effects. Satellite images show distinct clusters or 'nodes' of population, light, CO2, heat, and likely water vapour. These urban nodes juxtaposed with the intervening rural dark areas form a 'mosaic' perspective of the anthropogenic effects on climate. Over-averaging of these nodes to indicate a 'blanketing' effect and hiding the mosaic is likened to mis-diagnosing sharp appendicitis pain.

Near the surface of any neutron star there is a thin heat blanketing envelope that produces substantial thermal insulation of warm neutron star interiors and that relates the internal temperature of the star to its effective surface temperature. Physical processes in the blanketing envelopes are reasonably clear but the chemical composition is not. The latter circumstance complicates inferring physical parameters of matter in the stellar interiors from observations of the thermal surface radiation of the stars and urges one to elaborate the models of blanketing envelopes. We outline physical properties of these envelopes, particularly, the equation of state, thermal conduction, ion diffusion and others. Various models of heat blankets are reviewed, such as composed of separate layers of different elements, or containing diffusive binary ion mixtures in or out of diffusion equilibrium. The effects of strong magnetic fields in the envelopes are outlined as well as the effects of high temperatures which induce strong neutrino emission in the envelopes themselves. Finally, we discuss how the properties of the heat blankets affect thermal evolution of neutron stars and the ability to infer important information on internal structure of neutron stars from observations., Comment: 82 pages, 26 figures, accepted for publication in Physics Reports

(Abridged) Using the Zwicky Transient Facility alert stream, we are conducting a large campaign to spectroscopically classify all transients occurring in galaxies in the Census of the Local Universe (CLU) catalog. The aim of the experiment is to construct a spectroscopically complete, volume-limited sample of transients coincident within 100" of CLU galaxies out to 200 Mpc, and to a depth of 20 mag. We describe the survey design and spectroscopic completeness from the first 16 months of operations. We present results from a systematic search for Calcium rich gap transients in the sample of 22 low luminosity (peak absolute magnitude $M > -17$), hydrogen poor events found in the experiment (out of 754 spectroscopically classified SNe). We report the detection of eight Calcium rich gap transients, and constrain their volumetric rate to be at least $\approx 15\pm5$% of the SN Ia rate. Combining this sample with ten events from the literature, we find a likely continuum of spectroscopic properties ranging from events with SN Ia-like features (Ca-Ia objects) to SN Ib/c-like features (Ca-Ib/c objects) at peak light. Within the Ca-Ib/c events, we find two populations of events distinguished by their red ($g - r \approx 1.5$ mag) or green ($g - r \approx 0.5$ mag) spectral colors at $r$-band peak, wherein redder events show strong line blanketing signatures, slower light curves, weaker He lines and lower [Ca II]/[O I] in the nebular phase. Together, we find that the spectroscopic continuum, volumetric rates and striking old environments are consistent with the explosive burning of He shells on low mass white dwarfs. We posit that Ca-Ia and red Ca-Ib/c objects are consistent with the double detonation of He shells with high He burning efficiency, while green Ca-Ib/c objects could arise from less efficient He burning scenarios such as detonations in low density He shells or He shell deflagrations., 30 figures, 6 tables. Submitted to ApJ

The present study is the first of a series of three papers where we characterise the type II supernovae (SNe~II) from the Carnegie Supernova Project-I to understand their diversity in terms of progenitor and explosion properties. In this first paper, we present bolometric light curves of 74 SNe~II. We outline our methodology to calculate the bolometric luminosity, which consists of the integration of the observed fluxes in numerous photometric bands ($uBgVriYJH$) and black-body (BB) extrapolations to account for the unobserved flux at shorter and longer wavelengths. BB fits were performed using all available broadband data except when line blanketing effects appeared. Photometric bands bluer than $r$ that are affected by line blanketing were removed from the fit, which makes near-infrared (NIR) observations highly important to estimate reliable BB extrapolations to the infrared. BB fits without NIR data produce notably different bolometric light curves, and therefore different estimates of SN~II progenitor and explosion properties when data are modelled. We present two methods to address the absence of NIR observations: (a) colour-colour relationships from which NIR magnitudes can be estimated using optical colours, and (b) new prescriptions for bolometric corrections as a function of observed SN~II colours. Using our 74 SN~II bolometric light curves, we provide a full characterisation of their properties based on several observed parameters. We measured magnitudes at different epochs, as well as durations and decline rates of different phases of the evolution. An analysis of the light-curve parameter distributions was performed, finding a wide range and a continuous sequence of observed parameters which is consistent with previous analyses using optical light curves., Comment: Accepted for publication in A&A

We use reanalysis data and satellite remote sensing of cloud properties to examine how meteorological conditions alter the surface energy balance to cause surface melt that is detectable in satellite passive microwave imagery over West Antarctica. This analysis can detect each of the three primary mechanisms for inducing surface melt at a specific location: thermal blanketing involving sensible heat flux and/or longwave heating by optically thick cloud cover, all-wave radiative enhancement by optically thin cloud cover, and föhn winds. We examine case studies over Pine Island and Thwaites glaciers, which are of interest for ice shelf and ice sheet stability, and over Siple Dome, which is more readily accessible for field work. During January 2015 over Siple Dome we identified a melt event whose origin is an all-wave radiative enhancement by optically thin clouds. During December 2011 over Pine Island and Thwaites glaciers, we identified a melt event caused mainly by thermal blanketing from optically thick clouds. Over Siple Dome, those same 2011 synoptic conditions yielded a thermal-blanketing-driven melt event that was initiated by an impulse of sensible heat flux and then prolonged by cloud longwave heating. The December 2011 synoptic conditions also generated föhn winds at a location on the Ross Ice Shelf adjacent to the Transantarctic Mountains, and we analyze this case with additional support from automatic weather station data. In contrast, a late-summer thermal blanketing period over Pine Island and Thwaites glaciers during February 2013 showed surface melt initiated by cloud longwave heating and then prolonged by enhanced sensible heat flux. One limitation thus far with this type of analysis involves uncertainties in the cloud optical properties. Nevertheless, with improvements this type of analysis can enable quantitative prediction of atmospheric stress on the vulnerable Antarctic ice shelves in a steadily warming climate.

In equatorial regions, equatorial electrojet (EEJ) echoes often overlap with blanketing sporadic E (Esb) echoes. Also, Esb events could be classified as rare events over the Jicamarca Radio Observatory (JRO). For that reason, Esb identification is a big challenge for current software. Until now, the conventional method identifies Esb echoes visually. In this work, an innovative approach for automatic identification and observation of Esb events is presented. We developed an algorithm and implemented the first software to identify Esb events using image processing techniques and machine learning algorithms getting a sensitivity of 89%. We proposed a new criterion to identify Esb events taken into account the normal tendency of the F-layer minimum frequency due mainly to absorbance of the D region. We report the results of the first statistical study of Esb occurrence over JRO (11.95° S, 76.87° W and dip angle $\sim$ 1°) using the Digital Portable Sounder (DPS) - 4 Digisonde data from 2001 to 2018. We found Esb occurs mainly during the December solstice and also during minimum solar years. We observe the occurrence of Esb with a main peak at 1600 LT and a second peak around 0800 - 0900 LT. Furthermore, we obtained the ΔH between Jicamarca and Piura to measure the intensity of EEJ and counter electrojet (CEJ) and its behavior in time when Esb occurs. Finally, we discuss possible conditions that favor the formation of Esb.

Reworking of old sediment in the Murray-Darling implies alteration of environmental signals traveling from source to sink., Understanding how sediment transport and storage will delay, attenuate, and even erase the erosional signal of tectonic and climatic forcings has bearing on our ability to read and interpret the geologic record effectively. Here, we estimate sediment transit times in Australia’s largest river system, the Murray-Darling basin, by measuring downstream changes in cosmogenic 26Al/10Be/14C ratios in modern river sediment. Results show that the sediments have experienced multiple episodes of burial and reexposure, with cumulative lag times exceeding 1 Ma in the downstream reaches of the Murray and Darling rivers. Combined with low sediment supply rates and old sediment blanketing the landscape, we posit that sediment recycling in the Murray-Darling is an important and ongoing process that will substantially delay and alter signals of external environmental forcing transmitted from the sediment’s hinterland.

A new stratigraphic survey of the pyroclastic deposits blanketing Pompeii ruins shows departures from prior reconstruction of the events that occurred inside the town during the two main phases (pumice fallout and pyroclastic density currents) of the ad 79 Vesuvius eruption. We document the depth and distribution of subaerial erosion surfaces in the upper part of the pyroclastic sequence, formed during two short-lived breaks occurring in the course of the second phase of the eruption. These pauses could explain why 50% of the victims were found in the streets during the pyroclastic density currents phase.

The single-degenerate scenario for Type Ia supernovae (SNe Ia) should yield metal-rich ejecta that enclose some stripped material from the non-degenerate H-rich companion star. We present a large grid of non-local thermodynamic equilibrium steady-state radiative transfer calculations for such hybrid ejecta and provide analytical fits for the Halpha luminosity and equivalent width. Our set of models covers a range of masses for 56Ni and the ejecta, for the stripped material (Mst), and post-explosion epochs from 100 to 300d. The brightness contrast between stripped material and metal-rich ejecta challenges the detection of HI and HeI lines prior to ~100d. Intrinsic and extrinsic optical depth effects also influence the radiation emanating from the stripped material. This inner denser region is marginally thick in the continuum and optically thick in all Balmer lines. The overlying metal-rich ejecta blanket the inner regions, completely below about 5000A, and more sparsely at longer wavelengths. As a consequence, Hbeta should not be observed for all values of Mst through at least 300 days, while Halpha should be observed after ~100d for all Mst >= 0.01Msun. This contrasts with the case of circumstellar (CSM) interaction, not subject to external blanketing, which should produce Halpha and Hbeta lines with a strength dependent primarily on CSM density. We confirm previous analyses that suggest low values of order 0.001Msun for Mst to explain the observations of the two SNe Ia with nebular-phase Halpha detection, in conflict with the much greater stripped mass predicted by hydrodynamical simulations for the single-degenerate scenario. A more likely solution is the double-degenerate scenario, together with CSM interaction, or enclosed material from a tertiary star in a triple system or from a giant planet. [Abridged], Accepted for publication in A&A, references added in proofs

In the era of modern digital sky surveys, uncertainties in the flux of stellar standards are commonly the dominant systematic error in photometric calibration and can often affect the results of higher-level experiments. The Hubble Space Telescope (HST) spectrophotometry, which is based on computed model atmospheres for three hot (Teff > 30,000 K) pure-hydrogen (DA) white dwarfs, is currently considered the most reliable and internally consistent flux calibration. However many next generation facilities (e.g. Harmoni on E-ELT, Euclid and JWST) will focus on IR observations, a regime in which white dwarf calibration has not yet been robustly tested. Cool DA white dwarfs have energy distributions that peak close to the optical or near-IR, do not have shortcomings from UV metal line blanketing, and have a reasonably large sky density ($\simeq$ 4 deg$^{-2}$ at G < 20), making them, potentially, excellent calibrators. Here we present a pilot study based on STIS+WFC3 observations of two bright DA white dwarfs to test whether targets cooler than current hot primary standards (Teff < 20,000 K) are consistent with the HST flux scale. We also test the robustness of white dwarf models in the IR regime from an X-shooter analysis of Paschen lines and by cross-matching our previously derived Gaia white dwarf catalogue with observations obtained with 2MASS, UKIDSS, VHS, and WISE., 12 pages, 8 figures, 2 tables. Accepted for publication in MNRAS. The best fitting models to the two white dwarfs analyzed are available from \

This work analysis the blanketing sporadic layers (Es b ) behavior over Sao Luis, Brazil (2° 31′ S, 44° 16′ W, dip: −4.80) which is classified as a transition region between equatorial and low-latitude. Hence, some peculiarities can appear as Es b occurrence instead of the common Es q , which is a non-blanketing irregularity layer. The analysis presented here was obtained using a modified version of a theoretical model for the E region (MIRE), which computes the densities of the metallic ions (Fe + and Mg + ) and the densities of the main molecular ions (NO + , O 2 + , N 2 + ) by solving the continuity and momentum equations for each one of them. In that model, the Es layer physics driven by both diurnal and semidiurnal tidal winds are taken into account and it was extended in height coverage by adding a novel neutral wind model derived from the all-sky meteor radar measurements. Thus, we provide more trustworthy results related to the Es layer formation in the equatorial region. We verified the contribution of each tidal wind component to the Es b layer formation in this equatorial region. Additionally, we compared the Es layer electron density computed by MIRE with the data obtained by using the blanketing frequency parameter ( fb Es) deduced from ionograms. The results show that the diurnal component of the tidal wind is more important in the Es b layer formation whereas the semidiurnal component has a little contribution in our simulations. Finally, it was verified that the modified MIRE presented here can be used to study the Es b layers occurrence over the equatorial region in the Brazilian sector.

This work presents new results about sporadic E-layers (Es layers) using GPS (global positioning system) radio occultation (RO) measurements obtained from the FORMOSAT-3/COSMIC satellites and digisonde data. The RO profiles are used to study the Es layer occurrence as well as its intensity of the signal-to-noise ratio (SNR) of the 50 Hz GPS L1 signal. The methodology was applied to identify the Es layer on RO measurements over Cachoeira Paulista, a low-latitude station in the Brazilian region, in which the Es layer development is not driven tidal winds only as it is at middle latitudes. The coincident events were analyzed using the RO technique and ionosonde observations during the year 2014 to 2016. We used the electron density obtained using the blanketing frequency parameter (fbEs) and the Es layer height (h'Es) acquired from the ionograms to validate the satellite measurements. The comparative results show that the Es layer characteristics extracted from the RO measurements are in good agreement with the Es layer parameters from the digisonde. Keywords. Ionosphere (ionosphere–atmosphere interactions)

The tallest volcano in the solar system, Olympus Mons on Mars, is bordered by at least ten enormous sub-circular hummocky deposits forming a welded halo, termed the aureole. The aureole units (or simply aureoles), which are the deposits of landslides from Olympus Mons, have dramatically transformed the pristine size and shape of the volcanic edifice. Topographic data are used to determine the amount of collapsed material, and so reconstruct the original outline of Olympus Mons before the landslides took place, under the assumption that the edifice did not start failing until it had reached this maximum size. Due to post-aureole deposition on the eastern and southern flanks and to the uncertainty of the slippage level on the northern side, the reconstruction is sufficiently precise along the western and north-western Olympus Mons flank, it is more uncertain for the northern flank, while it is not feasible around the rest of the volcano. It appears that the radius along the western and north-western Olympus Mons before the collapse of the aureole landslides was approximately 200 km longer or more. The results show that the volume of the aureoles, even if enormous, is insufficient to fill the ideal conical edifice which would be obtained prolonging the Olympus Mons flanks with present slope angles. Thus, an overhang remains in the pre-aureole reconstructed Olympus Mons, which would also explain the onset of instability that led to the aureole collapse. Further, a drape deposit blanketing the southern Acheron Fossae ridge just at the front of the western (W) aureole landslide deposit and a fan-channel system carved on the same W aureole are investigated, and it is suggested that these morphologies have been emplaced in subaqueous setting. While the drape may indicate a landslide-thrust water splash akin to a tsunami deposit caused by the fast travelling W aureole landslide, the fan-channel system is similar to certain morphologies in the terrestrial oceans. A numerical model of the collapse of the western aureole unit in water shows final runouts on both Acheron ridge and Amazonis Planitia compatible with observations provided that the friction angle is extremely small, of the order of a tenth of degree. Simulations indicate that the W aureole could have reached Acheron Fossae ridge with velocities in excess of 100 m/s, which would explain the several tens of km long distance reached by the landslide-thrust tsunami deposit. In short, morphological and numerical lines of evidence would indicate a subaqueous origin for the largest, W aureole landslide.

Impact cratering is likely a primary agent of regolith generation on airless bodies. Regolith production via impact cratering has long been a key topic of study since the Apollo era. The evolution of regolith due to impact cratering, however, is not well understood. A better formulation is needed to help quantify the formation mechanism and timescale of regolith evolution. Here, we propose an analytically derived stochastic model that describes the evolution of regolith generated by small, simple craters. We account for ejecta blanketing as well as regolith infilling of the transient crater cavity. Our results show that the regolith infilling plays a key role in producing regolith. Our model demonstrates that, because of the stochastic nature of impact cratering, the regolith thickness varies laterally, which is consistent with earlier work. We apply this analytical model to the regolith evolution at the Apollo 15 site. The regolith thickness is computed considering the observed crater size-frequency distribution of small, simple lunar craters (< 381 m in radius for ejecta blanketing and < 100 m in radius for the regolith infilling). Allowing for some amount of regolith coming from the outside of the area, our result is consistent with an empirical result from the Apollo 15 seismic experiment. Finally, we find that the timescale of regolith growth is longer than that of crater equilibrium, implying that even if crater equilibrium is observed on a cratered surface, it is likely the regolith thickness is still evolving due to additional impact craters., 32 pages, 13 figures, 2 tables, and accepted for publication in JGR-Planets

The U BV photometry and low-resolution spectroscopy for the semiregular variable AI CMi, a candidate for post-AGB objects, performed in 1996–2016 and 2000–2013, respectively, are presented. The star showed multiperiodic brightness variations with an amplitude up to $$1\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{m} 5$$ in the V band, a significant (up to $$0\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{m} 4$$ ) bluing of the B − V and U − B colors as the star faded, and a change of its spectrum from G5 I to K3–5 I, depending on its brightness. A possible long-term fading of AI CMi below $$8\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{m} 5$$ in the period from May 2013 to early 2015 is observed in the light curve. The colors in this episode did not change the pattern of their unusual behavior with brightness. The main feature of the spectrum for AI CMi is the appearance and strengthening of TiO absorption bands as its brightness declines, which are atypical in the spectra of ordinary G5–K3 supergiants. The bluing of the B − V and U − B colors is interpreted as the blanketing of stellar radiation predominantly in V (and to a lesser extent in B) by the TiO absorption bands whose intensity increases dramatically with decreasing brightness. Another cause of the bluing can be the scattering of stellar radiation by small dust particles in the gas–dust shell of AI CMi. The star’s continuum-normalized spectra over the period from 2000 to 2013 in the wavelength range 4200 to 7700 or 9200 A are presented. These were taken at different phases of the pulsation cycle and clearly demonstrate the behavior of the TiO absorption bands depending on the V magnitude and B − V color. The equivalent widths of individual TiO bands weremeasured, and their correlation with the photometric parameters of the star is shown. AI CMi belongs to the O-rich branch of AGB/post-AGB supergiants and has a luminosity of ~4000 L ⊙ at a distance of 1500 ± 700 pc. The mass of AI CMi is most likely small and close to the lower mass limit for post-AGB stars. The connection of the star’s pulsational activity and nonstationary wind with the formation of its molecular and dust shells is discussed briefly.

This work presents new results about simulations of blanketing sporadic E-layers, Esb, using a modified version of a theoretical model for the E region (MIRE) for a Brazilian region: Cachoeira Paulista, a low latitude station. MIRE computes the densities of the metallic ions (Fe+ and Mg+) and of the main molecular ions (NO+, O2+, N2+) by solving the continuity and momentum equations for each one of them. Additionally, this model includes the physics of Es layer development driven by tidal winds. In this study, we extend MIRE adding a novel neutral wind model derived from the all-sky meteor radar measurements, which provides more trustworthy results related to the Es layer formation in the Brazilian sector. Afterwards, this new model is validated comparing the computed electron density for the Es layer with the electron density obtained using the blanketing frequency parameter (fbEs) deduced from ionograms in the analyzed region. The results show that the values computed by the extended MIRE are in good agreement with the observational data for the Es layers formed by the wind shear mechanism. Therefore, the extended MIRE presented in this work is the only available model that allows simulating Esb layers with a much higher confidence level for the low-latitude in the Brazilian sector.

The earliest history of the lunar dynamo is largely unknown and has important implications for the thermal state of the Moon and the physics of dynamo generation. The lunar sample with the oldest known paleomagnetic record is the 4.25 billion year old (Ga) troctolite 76535. Previous studies of unoriented subsamples of 76535 found evidence for a dynamo field with a paleointensity of several tens of microteslas. However, the lack of mutual subsample orientation prevented a demonstration that the magnetization was unidirectional, a key property of thermoremanent magnetization. Here we report further alternating field demagnetization on three mutually oriented subsamples of 76535, as well as new pressure remanent magnetization experiments to help rule out shock magnetization. We also describe new 40Ar/39Ar thermochronometry and cosmogenic neon measurements that better constrain the rock's thermal history. Although the rock is unbrecciated, unshocked, and slowly cooled, its demagnetization behavior is not ideal due to spurious remanence acquisition. Despite this limitation, all three subsamples record a high coercivity magnetization oriented in nearly the same direction, implying that they were magnetized by a unidirectional field on the Moon. We find no evidence for shock remanence, and our thermochronometry calculations show no significant reheating events since 4249 ± 12 million years ago (Ma). We infer a field paleointensity of approximately 20–40 μT, supporting the previous conclusion that a lunar dynamo existed at 4.25 Ga. The timing of this field supports an early dynamo powered by thermal or thermochemical core convection and/or a mechanical dynamo but marginally excludes a dynamo delayed by thermal blanketing from radiogenic element-rich magma ocean cumulates.

At first glance, the crops don't look any different from other crops blanketing the Salinas Valley, in California, which is often called "America's salad bowl." All you see are rows and rows of lettuce, broccoli, and cauliflower stretching to the horizon. But then the big orange robots roll through.

Submitted by Taís Silva (taismoreira001@gmail.com) on 2021-01-23T04:31:01Z No. of bitstreams: 1 CleristonFerreiraSilva.pdf: 13331769 bytes, checksum: ad09041842fb6f8cca3c2be64be62fed (MD5) Approved for entry into archive by Moreno Barros (moreno@ct.ufrj.br) on 2021-02-09T18:34:08Z (GMT) No. of bitstreams: 1 CleristonFerreiraSilva.pdf: 13331769 bytes, checksum: ad09041842fb6f8cca3c2be64be62fed (MD5) Made available in DSpace on 2021-02-09T18:34:08Z (GMT). No. of bitstreams: 1 CleristonFerreiraSilva.pdf: 13331769 bytes, checksum: ad09041842fb6f8cca3c2be64be62fed (MD5) Previous issue date: 2019-11 Foram investigados parâmetros que influenciam a magnitude do efeito blanketing relacionado à deposição dos sedimentos sobre o fluxo térmico no embasamento (QE). Foram simulados modelos 1D sintéticos e modelos 1D reais na Bacia de Santos, onde foram avaliados os efeitos do estiramento litosférico (β), da condutividade térmica, da taxa de sedimentação, e das espessuras de sedimentos rifte, de sal e do pós-sal. Para entender o efeito blanketing nas histórias térmicas das fases rifte e pós-rifte, os resultados dos modelos sintéticos e reais foram comparados com os resultados de um modelo termomecânico 1D sem o efeito blanketing. Os resultados mostraram que: (1) o QE no final da fase rifte diminui em 22% e 32% para respectivos β de 2 e de 6, considerando uma espessura sedimentar de 5,1 km; (2) o QE sempre é menor que o valor inicial pré – rifte decorridos cerca de 110 Ma após o final do rifteamento; (3) na porção proximal da Bacia de Santos, o QE decresce 36% em comparação ao modelo sem o efeito blanketing, uma vez que há altas taxas de sedimentação (∼ 150 m/Ma) e as espessuras sedimentares do pré-sal e pós-sal são aproximadamente de 3,5 km e de 4 km, respectivamente; (4) na porção distal da Bacia de Santos, onde as espessuras da seção pré-sal e pós-sal são ≤ 1,5 km e a espessura de sal é ≥ 3 km, o efeito blanketing é insignificante. Conclui-se que a magnitude do efeito blanketing no QE é relevante para situações com espessura sedimentar ≥ 3 km, condutividade térmicas ≤ 3,5 W/[m.K] e taxas de sedimentação ≥ 150 m/Ma. Portanto, recomenda-se considerar este efeito para situações semelhantes à porção proximal da Bacia de Santos. Entretanto, para regiões com espessura rifte delgada, e grandes espessuras de sal, pode-se considerar os QE providos dos modelos termomecânicos 1D. The blanketing effect is a effect of thermal insulation related to the deposition of cold sediments in a sedimentary basin that may affect its basement heat flow (BHF). We explored parameters that impact the magnitude of that effect through 1D simulations of synthetic and real case models from Santos Basin. The goal was to evaluate the role of lithospheric stretching (β), thermal conductivity, radiogenic heat generation, sedimentation rate, and sediment thicknesses of the pre-salt, salt, and post-salt packages in the magnitude of the blanketing effect. To better access the blanketing effect in the rift and post-rift phases, the results were compared to those calculated using 1D thermomechanical models without the blanketing effect. We observe that: (1) the BHF at the end of the rift stage decreases 22% and 32% if β is, respectively, 2 and 6, considering a sedimentary thickness of 5.1 km; (2) about 110 Myr after the end of the rift phase, BHF is always lower than the prerift BHF; (3) in the proximal area of Santos Basin, with high sedimentation rates (∼ 150 m/Ma), and pre- and post-salt sedimentary thicknesses of, respectively, 3,5 km and 4 km, the BHF decreases 36% compared to models calculated ignoring the blanketing effect; (4) in the distal Santos Basin, with pre- and post-salt thicknesses ≤ 1,5 km and salt layer ≥ 3 km-thick, the blanketing effect is insignificant. We conclude that the magnitude of the blanketing effect in the BHF should be taking into account in quantitative studies of areas with sedimentary thickness ≥ 3 km, thermal conductivity ≤ 3,5 W/m/K, and sedimentation rates ≥ 150 m/Ma. Thus, in areas with thin rift section and thick salt layer, one could use thermomechanical models. However, we suggest that the blanketing effect should be considered when evaluating areas similar to the proximal area of Santos Basin.

We analyze quantitatively the oxidative degradation of a sample in a cone-plate rheometer, as oxygen diffuses inward, radially, from the free boundary. We examine rheometer error mitigation by means of nitrogen blanketing, and also, of cone-plate partitioning. We arrive at exact analytical expressions for the oxygen concentration, and thus, for the degradation rate. We then integrate this rate over time to get the amount of oxygen reacted as a function of radial position and time in the degrading sample. To illustrate the usefulness of our analytical expressions, we provide two worked examples investigating the effect of nitrogen blanketing and cone-plate partitioning. We find that, though nitrogen blanketing always produces less degradation, its benefits are limited for short times. Additionally, cone-plate partitioning provides a simpler solution and allows samples to be run for longer times without degradation compromising measurement, even in samples initially saturated with oxygen. We close by considering the effect of antioxidants.

The detonation of a helium shell on a white dwarf has been proposed as a possible explosion triggering mechanism for Type Ia supernovae. Here, we report ZTF 18aaqeasu (SN 2018byg/ATLAS 18pqq), a peculiar Type I supernova, consistent with being a helium-shell double-detonation. With a rise time of $\approx 18$ days from explosion, the transient reached a peak absolute magnitude of $M_R \approx -18.2$ mag, exhibiting a light curve akin to sub-luminous SN 1991bg-like Type Ia supernovae, albeit with an unusually steep increase in brightness within a week from explosion. Spectra taken near peak light exhibit prominent Si absorption features together with an unusually red color ($g-r \approx 2$ mag) arising from nearly complete line blanketing of flux blue-wards of 5000 \AA. This behavior is unlike any previously observed thermonuclear transient. Nebular phase spectra taken at and after $\approx 30$ days from peak light reveal evidence of a thermonuclear detonation event dominated by Fe-group nucleosynthesis. We show that the peculiar properties of ZTF 18aaqeasu are consistent with the detonation of a massive ($\approx 0.15$ M$_\odot$) helium shell on a sub-Chandrasekhar mass ($\approx 0.75$ M$_\odot$) white dwarf after including mixing of $\approx 0.2$ M$_\odot$ of material in the outer ejecta. These observations provide evidence of a likely rare class of thermonuclear supernovae arising from detonations of massive helium shells., Comment: 10 pages, 6 figures. Submitted to ApJL

We present a numerical parameter survey of sub-Chandrasekhar mass white dwarf (WD) explosions. Carbon-oxygen WDs accreting a helium shell have the potential to explode in the sub-Chandrasekhar mass regime. Previous studies have shown how the ignition of a helium shell can either directly ignite the WD at the core-shell interface or propagate a shock wave into the the core causing a central ignition. We examine the explosions of WDs from 0.6 - 1.2 M$_\odot$ with helium shells of 0.01, 0.05 and 0.08 M$_\odot$. Distinct observational signatures of sub-Chandrasekhar mass WD explosions are predicted for two categories of shell size. Thicker-shell models show an early time flux excess, which is caused by the presence of radioactive material in the ashes of the helium shell, and red colors due to these ashes creating significant line blanketing in the UV through the blue portion of the spectrum. Thin shell models reproduce several typical Type Ia supernova signatures. We identify a relationship between Si II velocity and luminosity which, for the first time, identifies a sub-class of observed supernovae that are consistent with these models. This sub-class is further delineated by the absence of carbon in their atmospheres. We suggest that the proposed difference in the ratio of selective to total extinction between the high velocity and normal velocity Type Ia supernovae is not due to differences in the properties of the dust around these events, but is rather an artifact of applying a single extinction correction to two intrinsically different populations of supernovae., 13 pages, 12 figures, Accepted to ApJ 30 Decemeber 2018

We analyze quantitatively the oxidative degradation of a sample in a parallel-disk rheometer, as oxygen diffuses inward, radially, from the free boundary. We examine rheometer error mitigation by means of nitrogen blanketing, and also, of parallel-disk partitioning. We arrive at exact analytical expressions for the oxygen concentration and, thus, for the degradation rate. We then integrate this rate over time to get the amount of oxygen reacted as a function of radial position and time in the degrading sample. To illustrate the usefulness of our analytical expressions, we provide two worked examples investigating the effect of nitrogen blanketing and parallel-disk partitioning. We find that, though nitrogen blanketing always produces less degradation, its benefits are limited for short times. Additionally, parallel-disk partitioning provides a simpler solution and allows samples to be run for longer times without degradation compromising measurement, even in samples initially saturated with oxygen. We also consider the effect of antioxidants. We also consider an important special case, without chemical reaction, where the sample dries by evaporation from its free surface. We close by comparing the roles played by polymer degradation in parallel-disk flow versus cone-plate flow.

We study the effects of heat blanketing envelopes of neutron stars on their cooling. To this aim, we perform cooling simulations using newly constructed models of the envelopes composed of binary ion mixtures (H--He, He--C, C--Fe) varying the mass of lighter ions (H, He or C) in the envelope. The results are compared with those calculated using the standard models of the envelopes which contain the layers of lighter (accreted) elements (H, He and C) on top of the Fe layer, varying the mass of accreted elements. The main effect is that the chemical composition of the envelopes influences their thermal conductivity and, hence, thermal insulation of the star. For illustration, we apply these results to estimate the internal temperature of the Vela pulsar and to study the cooling of neutron stars of ages of 0.1 - 1 Myr at the photon cooling stage. The uncertainties of the cooling models associated with our poor knowledge of chemical composition of the heat insulating envelopes strongly complicate theoretical reconstruction of the internal structure of cooling neutron stars from observations of their thermal surface emission., 8 pages, 4 figures, MNRAS, accepted

A comprehensive investigation of spread F irregularities over Indian sector has been carried out using VHF radar and ionosonde observations. Two different categories of spread F observations, one where the onset of the range spread F (RSF) was concurrent with the peak h'F (category1), and another where the RSF onset happened ~90 minutes after the peak h'F time (category2) are presented. RSF in category2 was preceded by the presence of oblique echoes in ionograms, indicating the irregularity genesis westward of Sriharikota. The average peak h'F in category1 was ~30 km higher than that in category2 indicating the presence of standing large scale wave structure (LSWS). Occurrence of the blanketing Es during 19:30 to 20:30 IST (Indian Standard Time) in category1 (category 2) was 0% (>50%). Model computation is also carried out to further substantiate the observational results. Model computation indicates that zonal variation of low latitude Es can generate zonal modulation in the F layer height rise. It is found that the modulation of the F layer height, linked with the low latitude Es, assists the equatorial spread F (ESF) onset by modifying both, growth rate of the collisional Rayleigh-Taylor (RT) instability and also its efficiency. Although, a predominant presence of low latitude Es has been observed, but the increase in the F layer height and the RT instability growth in the evening hours will maximize with complete absence of low latitude Es. A new mechanism for the generation of LSWS and its implications on RT instability is discussed.

Dead-ended anode operation has a number of practical advantages that simplify system complexity and lower cost for polymer electrolyte fuel cells. However, dead-ended mode leads to performance loss over time which can only be reversed by performing intermittent purge events. This work applies a combined hydro-electro-thermal analysis to an air-cooled open-cathode fuel cell, presenting experimental functional maps of water distribution, current density and temperature. This approach has allowed the identification of a ‘nitrogen blanketing’ effect due to nitrogen cross-over from the cathode and a ‘bypass’ effect where a peripheral gap between the gasket and the GDL offers a hydrogen flow ‘short circuit’ to the border of the electrode. A consequence of high local current density at the margin of the electrode, and resulting high temperatures, may impact the lifetime of the cell in dead-end mode.

In this work a method has been presented for preparation of sol–gel derived transparent conductive Al-doped zinc oxide (AZO) films. This method is based on rapid cooling of the glass in the presence of a gas blanket and does not require the post annealing step. Rapid cooling is used to kinetically limit the oxygen diffusion to the film and gas blanketing has been used to enhance the effect. Gas blankets have been generated by placing the hot AZO coated glass on a gas evolving material (e.g. ammonium carbonate) which generates gas by endothermic reaction. Rapid cooling has been shown to be only slightly effective and combined rapid cooling and gas blanketing has been shown to be a good combination. AZO films (100 nm thick) prepared by this method show low resistivity (5.4 × 10 − 2 Ω ‐ cm), high transmittance (> 90%), and preferential crystalline orientation [002] comparable with conventionally post-annealed AZO film in forming gas atmosphere.

We construct new models of outer heat blanketing envelopes of neutron stars composed of binary ion mixtures (H - He, He - C, C - Fe) in and out of diffusive equilibrium. To this aim, we generalize our previous work on diffusion of ions in isothermal gaseous or Coulomb liquid plasmas to handle non-isothermal systems. We calculate the relations between the effective surface temperature Ts and the temperature Tb at the bottom of heat blanketing envelopes (at a density rhob= 1e8 -- 1e10 g/cc) for diffusively equilibrated and non-equilibrated distributions of ion species at different masses DeltaM of lighter ions in the envelope. Our principal result is that the Ts - Tb relations are fairly insensitive to detailed distribution of ion fractions over the envelope (diffusively equilibrated or not) and depend almost solely on DeltaM. The obtained relations are approximated by analytic expressions which are convenient for modeling the evolution of neutron stars., Comment: 12 pages, 7 figures, MNRAS, published

The oxidation of oil starts, in general, from the penetration of atmospheric oxygen into oil. Inhibition of the vigorous oxidation of oil at deep-frying temperature under carbon dioxide flow, by disrupting the contact between oil and air, was first demonstrated using oil in a round bottom flask. Next, the minimum carbon dioxide flow rate necessary to blanket 4 L of frying oil in an electric fryer (surface area 690 cm(2)) installed with nonwoven fabric cover, was found to be 40 L/h. Then deep-frying of potato was done accordingly; immediately after deep-frying, an aluminum cover was placed on top of the nonwoven fabric cover to prevent the loss of carbon dioxide and the carbon dioxide flow was shut off. In conclusion, the oxidation of oil both at deep-frying temperature and during standing was remarkably inhibited by carbon dioxide blanketing at a practical flow rate and volume. Under the deep-frying conditions employed in this study, the increase in polar compound content was reduced to half of that of the control.

The ordinary wave critical frequency foEs is measured routinely by ionosondes and used widely in estimating the intensity and occurrence of sporadic E (Es) metal ion layers. Recently, however, it was realized that foEs overestimates Es intensities because it corresponds to the sum of both the layer metal ion plasma and the regular E region plasma densities. To account for this, a new parameter, foμEs, was introduced that corresponds to the Es layer metal plasma density only, and a method was proposed for its calculation. In the present work, an ionosonde data set is analyzed to assess the importance of replacing foEs by foμEs in Es studies. To this objective, the diurnal and seasonal variability of sporadic E is re-examined. It turns out that the Es mean diurnal and seasonal variations estimated by means of using foμEs, differ substantially from those based on foEs, implying that the use of foEs leads to biased results and wrong physical inferences. It is therefore urged that foμEs is adopted and used instead of foEs, in future ionosonde sporadic E studies. The same applies for the case of satellite radio occultation (RO) sporadic E investigations as well, where foμEs should be used, instead of foEs, for calibration and validation purposes. All this is equally valid in the case of the blanketing sporadic E frequency fbEs and the corresponding new parameter fbμEs that needs also to be adopted and used.

The tritium storage bed receives and supplies tritium gas for fusion facilities. Inert gases, such as helium-3, which is produced by tritium beta decay, disturb the absorption behavior of tritium in the bed and this is called the Helium Blanketing Effect (HBE). This study focused on the HBE and gas circulation as a way of breaking the HBE for the hydriding reaction with ZrCo. The hydriding reaction with the application of 100 % hydrogen without helium-4 was completed within five minutes under 120 kPa initial hydrogen partial pressure and 20 °C reactor temperature. With 5% helium-4 in the hydrogen, it took more than 1000 min for the hydriding reaction to be completed under the same conditions. The HBE was broken with the application of a gas-circulation process. Even with 50 % helium-4 in the hydrogen, the hydriding reaction was completed in five minutes under the same conditions. In an experiment conducted at various flow rates of gas circulation, breaking the HBE was observed even at a small flow rate. The gas circulation process can efficiently break the HBE and separate the helium-3 produced in the tritium storage bed.

A multi-year global comparison between mid-latitude and equatorial sporadic-E ( E s ) height and intensity derived from COSMIC GPS radio occultation (GPS-RO) data and blanketing E frequency (fbEs) from ground-based Digisonde measurements is performed. The E s layer intensity from GPS-RO measurements was estimated using the S2 scintillation index and total electron content (TEC) assuming constant and variable E s cloud thicknesses individually. GPS-RO crossings were limited to within 150 km and 30 min of fbEs occurrences at each Digisonde. Intensities derived from the TEC with constant thickness method agreed more closely with the Digisonde fbEs measurements in terms of relative error and spread. E s path lengths estimated from the variable thickness method were also significantly larger than the average E s cloud length indicating that tube geometry assumptions between thickness and length do not apply to sporadic-E. Furthermore, intensities calculated from the S2 technique generally placed the frequency of fbEs between 2.7 and 5.3 MHz. Mean fbEs predictions from the S2 and constant thickness TEC methods are found to be statistically similar to the mean Digisonde fbEs. Both TEC and S2 methods underestimated the altitude of the fbEs events, but the S2 technique performed better overall. The mean heights calculated from both of the GPS-RO methods show a statistically significant difference with the mean Digisonde calculated heights, suggesting a bias in the height estimates.

The geothermal zone of southeast China, which is one of the country&rsquo, s known geothermal zones, contains significant natural geothermal resources. To understand the formation of geothermal resources, a magnetotelluric (MT) investigation with a site spacing of 1&ndash, 2 km was carried out around the Zhangzhou Basin. The recorded MT data were processed by robust time series and remote reference processing techniques. The data analysis results revealed that two-dimensional (2-D) modeling can be used to approximately determine the electrical structure. The joint inversions of TE and TM modes have been performed after distortion decomposition. In the inversion models, a low resistivity cap of 200&ndash, 800 m thickness was observed, which represented the blanketing sediments composed of Quaternary and volcanic rocks of the late Jurassic period. The presence of high resistivity above a depth of 20 km indicates the granites are widely developed in the upper and middle crust. MT measurements have revealed some deep-seated high conductive zones, which were inferred to be partially melting at depth of 8&ndash, 17 km, which is likely to be reason behind the formation of higher-temperature hot springs. The results also show that there is a shallower Moho, which indicates that the heat from the upper mantle may have a big contribution to the surface heat flow. Fractures-controlled meteoric fluid circulation is the most likely explanation for the hot springs.

We present a high resolution synthetic spectral library, INTRIGOSS, designed for studying FGK stars. The library is based on atmosphere models computed with specified individual element abundances via ATLAS12 code. Normalized SPectra (NSP) and surface Flux SPectra (FSP), in the 4830-5400 A, wavelength range, were computed with the SPECTRUM code. INTRIGOSS uses the solar composition by Grevesse et al. 2007 and four [alpha/Fe] abundance ratios and consists of 15,232 spectra. The synthetic spectra are computed with astrophysical gf-values derived by comparing synthetic predictions with a very high SNR solar spectrum and the UVES-U580 spectra of five cool giants. The validity of the NSPs is assessed by using the UVES-U580 spectra of 2212 stars observed in the framework of the Gaia-ESO Survey and characterized by homogeneous and accurate atmospheric parameter values and by detailed chemical compositions. The greater accuracy of NSPs with respect to spectra from the AMBRE, GES_Grid, PHOENIX, C14, and B17 synthetic spectral libraries is demonstrated by evaluating the consistency of the predictions of the different libraries for the UVES-U580 sample stars. The validity of the FSPs is checked by comparing their prediction with both observed spectral energy distribution and spectral indices. The comparison of FSPs with SEDs derived from ELODIE, INDO--U.S., and MILES libraries indicates that the former reproduce the observed flux distributions within a few percent and without any systematic trend. The good agreement between observational and synthetic Lick/SDSS indices shows that the predicted blanketing of FSPs well reproduces the observed one, thus confirming the reliability of INTRIGOSS FSPs., 32 pages, 12 figures