Cepheid stars play a considerable role as extragalactic distances indicators, thanks to the simple empirical relation between their pulsation period and their luminosity. They overlap with that of ...secondary distance indicators, such as Type Ia supernovae, whose distance scale is tied to Cepheid luminosities. However, the period-luminosity (P-L) relation still lacks a calibration to better than 5%. Using an original combination of interferometric astrometry with optical and ultraviolet spectroscopy, we measured the geometrical distance pc of the 3.33 day period Cepheid V1334 Cyg with an unprecedented accuracy of 1%, providing the most accurate distance for a Cepheid. Placing this star in the P-L diagram provides an independent test of existing P-L relations. We show that the secondary star has a significant impact on the integrated magnitude, particularly at visible wavelengths. Binarity in future high-precision calibrations of the P-L relations is not negligible, at least in the short-period regime. Subtracting the companion flux leaves V1334 Cyg in marginal agreement with existing photometric-based P-L relations, indicating either an overall calibration bias or a significant intrinsic dispersion at a few percent level. Our work also enabled us to determine the dynamical masses of both components, (Cepheid) and (companion), providing the most accurate masses for a Galactic binary Cepheid system.
High angular resolution images of IRC+10216 are presented in several near-infrared wavelengths spanning more than 8 years. These maps have been reconstructed from interferometric observations ...obtained at both Keck and the VLT, and also from stellar occultations by the rings of Saturn observed with the Cassini spacecraft. The dynamic inner regions of the circumstellar environment are monitored over eight epochs ranging between 2000 January and 2008 July. The system is shown to experience substantial evolution within this period including the fading of many previously reported persistent features, some of which had been identified as the stellar photosphere. These changes are discussed in the context of existing models for the nature of the underlying star and the circumstellar environment. With access to these new images, we are able to report that none of the previously identified bright spots in fact contains the star, which is buried in its own dust and not directly visible in the near-infrared.
Background
Line‐field confocal optical coherence tomography (LC‐OCT) is a non‐invasive optical technique recently developed for skin examination in vivo. It provides real‐time, high‐resolution ...vertical images with an isotropic resolution of ~1 µm and a penetration depth of ~500 µm.
Objectives
Study goals were to qualitatively/quantitatively characterize healthy skin at different body sites using LC‐OCT.
Methods
The skin of young healthy volunteers was imaged with a handheld LC‐OCT imaging device. Seven body sites (back of the hand, forehead, cheek, nose, chest, forearm and back) were investigated. An independent qualitative cutaneous structures' description; visibility of keratinocytes' nuclei and dermal–epidermal junction (DEJ) and quantitative stratum corneum (SC)/epidermal thicknesses; height of dermal papillae assessment of the LC‐OCT images was performed.
Results
A total of 88 LC‐OCT images were collected from 29 participants (20 females; nine males; mean age 25.9 years). Keratinocytes' nuclei and DEJ were visible in the totality of images. The different layers of the epidermis and the remaining cutaneous structures/findings were visualized. Body sites‐related variability was detected for SC/epidermal thicknesses and height of dermal papillae. Inter‐observer agreement was excellent (SC thickness), good‐to‐excellent (epidermal thickness) and moderate‐to‐good (papillae).
Conclusions
Line‐field confocal‐OCT provides non‐invasive, real‐time imaging of the skin in vivo with deep penetration and high resolution, enabling the visualization of single cells. The histology‐like vertical view provides an easy way to recognize/measure different cutaneous structures/findings. LC‐OCT appears as a promising technique for the examination of physiological/pathological skin.
To improve the performances of Nickel–Metal Hydride batteries, an important step is the understanding of the corrosion processes that take place in the electrode material. In particular, the present ...study focuses for the first time on the model (La, Mg)2Ni7 system. The calendar corrosion in 8.7 M KOH medium was investigated from 6 h to 16 weeks immersion. By a unique combination of structural and elemental characterisations, the corrosion products are evidenced in those systems. In particular, we demonstrate that Ni and Mg combine in a pseudo-binary hydroxide Mg1−xNix(OH)2 whereas La corrodes into nanoporous La(OH)3 needles with inner hollow nanochannels.
EDX-STEM mapping on La1.5Mg0.5Ni7 sample corroded 8 weeks: correlation of Mg and Ni distribution. Display omitted
•The calendar corrosion of Ni–MH battery alloy system (La, Mg)2Ni7 is investigated.•Combination of μRaman and TEM allows full characterisation of corrosion products.•Influence of Mg substitution in the binary La2Ni7 on corrosion is demonstrated.•La corrodes as La(OH)3 needles with inner hollow nanochannels.•The formation of a pseudo-binary hydroxide Mg1−xNix(OH)2 is evidenced.
Background
Early diagnosis and subtype classification of basal cell carcinoma (BCC) are crucial to reduce morbidity and optimize treatment. Good accuracy in differentiating BCC from clinical ...imitators has been achieved with existing diagnostic strategies but lower performance in discriminating BCC subtypes. Line‐field confocal optical coherence tomography (LC‐OCT) is a new technology able to combine the technical advantages of reflectance confocal microscopy and OCT.
Objectives
To identify and describe LC‐OCT criteria associated with BCC and explore their association with BCC subtypes.
Methods
Basal cell carcinoma were imaged with a handheld LC‐OCT device before surgical excision. LC‐OCT images were retrospectively evaluated by three observers for presence/absence of criteria for BCC. Multivariate logistic regression models were used to find independent predictors of BCC subtypes.
Results
Eighty‐nine histopathologically proven BCCs were included, of which 66 (74.2%) were pure subtypes superficial BCC (sBCC): 19/66 (28.8%); nodular BCC (nBCC): 31/66 (47.0%); infiltrative BCC (iBCC): 16/66 (24.2%). Lobules, blood vessels and small bright cells within epidermis/lobules were the most frequent criteria for BCC. LC‐OCT criteria independently associated with sBCC were presence of hemispheric lobules, absence of lobule separation from the epidermis, absence of stretching of the stroma; with nBCC were presence of macrolobules, absence of lobule connection to the epidermis; and with iBCC were presence of branched lobules.
Conclusions
This was the first study describing the characteristics of BCC under LC‐OCT examination. We proposed morphologic criteria, which could be potentially useful for diagnosis and subtype classification of BCC, as well as for its therapeutic management. Future studies are needed to assess these hypotheses.
Abstract
Millimeter observations of disks around young stars reveal substructures indicative of gas pressure traps that may aid grain growth and planet formation. We present Submillimeter Array ...observations of HD 34700: two Herbig Ae stars in a close binary system (Aa/Ab, ∼0.25 au), surrounded by a disk presenting a large cavity and spiral arms seen in scattered light, and two distant, lower-mass companions. These observations include 1.3 mm continuum emission and the
12
CO 2–1 line at ∼05 (178 au) resolution. They resolve a prominent azimuthal asymmetry in the continuum and Keplerian rotation of a circumbinary disk in the
12
CO line. The asymmetry is located at a radius of 155
+11
−7
au, consistent with the edge of the scattered-light cavity, being resolved in both radius (72
+14
−15
au) and azimuth (FWHM = 64
°+8
−7
). The strong asymmetry in millimeter continuum emission could be evidence for a dust trap, together with the more symmetric morphology of
12
CO emission and small grains. We hypothesize an unseen circumbinary companion responsible for the cavity in scattered light and creating a vortex at the cavity edge that manifests in dust trapping. The disk mass has limitations imposed by the detection of
12
CO and nondetection of
13
CO. We discuss its consequences for the potential past gravitational instability of this system, likely accounting for the rapid formation of a circumbinary companion. We also report the discovery of resolved continuum emission associated with HD 34700B (projected separation ∼1850 au), which we explain through a circumstellar disk.
Aims. This paper reports on H-band interferometric observations of Betelgeuse made at the three-telescope interferometer IOTA. We image Betelgeuse and its asymmetries to understand the spatial ...variation of the photosphere, including its diameter, limb darkening, effective temperature, surrounding brightness, and bright (or dark) star spots. Methods. We used different theoretical simulations of the photosphere and dusty environment to model the visibility data. We made images with parametric modeling and two image reconstruction algorithms: MIRA and WISARD. Results. We measure an average limb-darkened diameter of 44.28 ± 0.15 mas with linear and quadratic models and a Rosseland diameter of 45.03 ± 0.12 mas with a MARCS model. These measurements lead us to derive an updated effective temperature of 3600 ± 66 K. We detect a fully-resolved environment to which the silicate dust shell is likely to contribute. By using two imaging reconstruction algorithms, we unveiled two bright spots on the surface of Betelgeuse. One spot has a diameter of about 11 mas and accounts for about 8.5% of the total flux. The second one is unresolved (diameter < 9 mas) with 4.5% of the total flux. Conclusions. Resolved images of Betelgeuse in the H band are asymmetric at the level of a few percent. The MOLsphere is not detected in this wavelength range. The amount of measured limb-darkening is in good agreement with model predictions. The two spots imaged at the surface of the star are potential signatures of convective cells.
Aims.
We aim to demonstrate that the presence and mass of an exoplanet can now be effectively derived from the astrometry of another exoplanet.
Methods.
We combined previous astrometry of
β
Pictoris ...b with a new set of observations from the GRAVITY interferometer. The orbital motion of
β
Pictoris b is fit using Markov chain Monte Carlo simulations in Jacobi coordinates. The inner planet,
β
Pictoris c, was also reobserved at a separation of 96 mas, confirming the previous orbital estimations.
Results.
From the astrometry of planet b only, we can (i) detect the presence of
β
Pictoris c and (ii) constrain its mass to 10.04
−3.10
+4.53
M
Jup
. If one adds the astrometry of
β
Pictoris c, the mass is narrowed down to 9.15
−1.06
+1.08
M
Jup
. The inclusion of radial velocity measurements does not affect the orbital parameters significantly, but it does slightly decrease the mass estimate to 8.89
−0.75
+0.75
M
Jup
. With a semimajor axis of 2.68 ± 0.02 au, a period of 1221 ± 15 days, and an eccentricity of 0.32 ± 0.02, the orbital parameters of
β
Pictoris c are now constrained as precisely as those of
β
Pictoris b. The orbital configuration is compatible with a high-order mean-motion resonance (7:1). The impact of the resonance on the planets’ dynamics would then be negligible with respect to the secular perturbations, which might have played an important role in the eccentricity excitation of the outer planet.
•We took into account all the reviewer#4 remarks and requirements.•Also, we have corrected all the minor points mentioned.•You will find all details in the point-to-point answers document.
The 2D ...shallow water equations adequately model some geophysical flows with wet-dry fronts (e.g. flood plain or tidal flows); nevertheless deriving accurate, robust and conservative numerical schemes for dynamic wet-dry fronts over complex topographies remains a challenge. Furthermore for these flows, data are generally complex, multi-scale and uncertain. Robust variational inverse algorithms, providing sensitivity maps and data assimilation processes may contribute to breakthrough shallow wet-dry front dynamics modelling. The present study aims at deriving an accurate, positive and stable finite volume scheme in presence of dynamic wet-dry fronts, and some corresponding inverse computational algorithms (variational approach). The schemes and algorithms are assessed on classical and original benchmarks plus a real flood plain test case (Lèze river, France). Original sensitivity maps with respect to the (friction, topography) pair are performed and discussed. The identification of inflow discharges (time series) or friction coefficients (spatially distributed parameters) demonstrate the algorithms efficiency.
The forthcoming Surface Water and Ocean Topography (SWOT) satellite mission will provide global measurements of the free surface of large rivers, providing new opportunities for remote ...sensing‐derived estimates of river discharge in gaged and ungaged basins. SWOT discharge algorithms have been developed and benchmarked using synthetic data but remain untested on real‐world swath altimetry observations. We present the first discharge estimates from AirSWOT, a SWOT‐like airborne Ka‐band radar, using 6 days of measurements over a 40‐km segment of the Willamette River in Oregon, USA. The three evaluated discharge algorithms estimated discharge with normalized root‐mean‐square errors of 10–31% when compared with in situ gage data but were sensitive to an initial estimate of mean annual discharge. Our results show that these discharge algorithms provide reliable discharge estimates on remotely sensed data at SWOT‐like spatial scales while highlighting the need for further algorithm sensitivity tests.
Plain Language Summary
River discharge is a key element of the water cycle, but river gaging networks have significant gaps at the global scale. In 2021, the Surface Water and Ocean Topography (SWOT) mission will be launched to collect high‐accuracy measurements of the world's surface waters, including all global rivers wider than 100 m. In anticipation of SWOT, methods to estimate discharge from its measurements have been developed but have yet to be tested on real‐world data at the spatial scales and accuracies expected of SWOT. We test three such discharge algorithms on data collected by AirSWOT, an airborne variant of SWOT, as it flew over the Willamette River in Oregon, USA. We show that river discharge can be estimated by these algorithms with encouraging accuracy (10–31%) using only airborne measurements and a model‐derived estimate of the mean annual discharge. We stress the need for further testing of these algorithms to determine their sensitivities to the initial estimate of flow and the hydraulic character of the river reach but suggest that these results are encouraging for future global‐scale deployment of SWOT discharge algorithms.
Key Points
River discharge is estimated using solely swath altimetry for the first time
Three discharge algorithms which have been developed and tested on in‐situ or synthetic datasets yield normalized errors of 10–31 %
Algorithm accuracies are encouraging for the forthcoming SWOT satellite mission but show a strong dependence on prior information
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