Multi-passband Observations of a Solar Flare over the He i 10830 Å line

This study presents a C3.0 flare observed by the Big Bear Solar Observatory/Goode Solar Telescope (GST) and Interface Region Imaging Spectrograph (IRIS) on 2018 May 28 around 17:10 UT. The Near-Infrared Imaging Spectropolarimeter of GST was set to spectral imaging mode to scan five spectral positions at ±0.8, ±0.4 Å and line center of He i 10830 Å. At the flare ribbon’s leading edge, the line is observed to undergo enhanced absorption, while the rest of the ribbon is observed to be in emission. When in emission, the contrast compared to the preflare ranges from about 30% to nearly 100% at different spectral positions. Two types of spectra, “convex” shape with higher intensity at line core and “concave” shape with higher emission in the line wings, are found at the trailing and peak flaring areas, respectively. On the ribbon front, negative contrasts, or enhanced absorption, of about ∼10%–20% appear in all five wavelengths. This observation strongly suggests that the negative flares observed in He i 10830 Å with mono-filtergram previously were not caused by pure Doppler shifts of this spectral line. Instead, the enhanced absorption appears to be a consequence of flare-energy injection, namely nonthermal collisional ionization of helium caused by the precipitation of high-energy electrons, as found in our recent numerical modeling results. In addition, though not strictly simultaneous, observations of Mg ii from the IRIS spacecraft, show an obvious central reversal pattern at the locations where enhanced absorption of He i 10830 Å is seen, which is consistent with previous observations.

Estimation of Shear-Wave Velocity Structures in Taichung, Taiwan, Using Array Measurements of Microtremors

Near-surface S-wave velocity structures (VS) are crucial in site-effect studies and ground-motion simulations or predictions. We explored S-wave velocity structures in Taichung, the second-largest city in Taiwan by population, by employing array measurements of microtremors at a total of 53 sites. First, the fundamental-mode dispersion curves of Rayleigh waves were estimated by adopting the frequency–wavenumber analysis method. Second, the surface-wave inversion technique was used to calculate the S-wave velocity structures of the area. At many sites, observed phase velocities were almost flat, with a phase velocity of approximately 800–1300 m/s in the frequency range of 0.6–2 Hz. A high-velocity zone (VS of 900–1500 m/s) with a convex shape was observed at the shallow S-wave structures of these sites (depths of 50–500 m). On the basis of the inversion results, we constructed two-dimensional and three-dimensional contour maps to elucidate the variations of VS structures in Taichung. According to VS-contour maps at different depths, lowest S-wave velocities are found at the western coastal plain, whereas highest S-wave velocities appear on the eastern side. The S-wave velocity gradually decreases from east to west. Moreover, the S-wave velocity of the Tertiary bedrock is assumed to be 1500 m/s in the area. According to the depth-contour map (VS = 1500 m/s), the depths of the bedrock range from 250 m (the eastern part) to 1550 m (the western part). The thicknesses of the alluvium gradually decrease from west to east. Our results are consistent with the geology of the Taichung area.

What do Biphasic Flow Experiments Reveal On the Variability of Exposure on Alluvial Fans and Which Implications for Risk Assessment Result From This?

Autogenic processes, such as sudden avulsions, unexpected channel migrations and backfilling phenomena, can considerably alter the propagation of sediment-laden flows on alluvial fans. Once the initial and boundary conditions of the hazard scenario with a given return period are determined, the delineation of the associated exposed areas is based on one numerical, essentially deterministic, process simulation, which may not adequately reflect the underlying process variability. By following a ‘similarity-of-process concept’ we generated sediment-laden flows on an experimental alluvial fan. Thereby, we considered an alluvial fan model layout with a curved guiding channel and featuring a convex shape. As loading conditions, we defined a reference, an increased and a reduced level for the released water volume and the predisposed solid fraction. Further, we imposed two different stream power regimes and executed, for each factor combination, eight experimental runs. The associated exposure areas were recorded by video and were mapped in a GIS. We then analyzed exposure data and derived exposure probability maps superposing the footprints of the eight repetitions generated by each experimental loading condition. The patterns of exposure associated with specific loading conditions showed a noticeable variability due to the main effect of the total event volume, the solid fraction and the interactions between them and with the imposed stream power in the feeding channel. Our research highlights that a probabilistic notion of exposure in risk assessment and mitigation needs to be considered. Further, a major challenge consists in adapting numerical codes to better mirror the stochastics of process propagation for more reliable flood hazard and risk assessments.

Anatomical and histochemical characterization of leaves of Spondias purpurea L.

The Anacardiaceae family has species rich in secondary metabolites. They are widely used in popular medicine. Among them, Spondias purpurea L. stands out for containing several secondary metabolites with important biological activities. To aid in the precise identification of the species, this work aims to perform an anatomical and histochemical characterization of leaves of S. purpurea. Microscope slides containing cross-sections of the petiolule and leaflets, in addition to paradermal sections of the leaflets, were prepared and analyzed in an optical and polarized microscope. Histochemical tests were performed on fresh leaflets. Through microscopic analysis, it was possible to identify the anatomical structures that allow the diagnosis of the studied species, such as petiolule with concave-convex shape, non-glandular and glandular trichomes, druses in phloem; leafletsamphistomatic, with non-glandular trichomes on the adaxial face and glandular trichomes on the abaxial face, midrib with concave-convex shape, two collateral vascular bundles, one layer of palisade parenchyma, druses in phloem and mesophyll. Through histochemistry, the presence of phenolic compounds, alkaloids, tannins, triterpenes, steroids, lipophilic compounds, essential oils, lignin, starch and calcium oxalate crystals were evidenced in the leaflets. The results are important for the quality control of plant material.

Influence of the Shape of the First Metatarsal Cuneiform Joint on the Development of Hallux Valgus Deformity

Objective:To examine the presence of certain shapes of the first metatarsal-cuneiform joint (MTC) joint in feet with hallux valgus (HV) deformity. To determine whether the anatomical orientation of this joint affects the size of the hallux valgus angle (HVA) and the first intermetatarsal angle (IMA) and whether it contributes to the dynamics of the developmental course of HV deformity.Methods:The shape of the first MTC joint was determined on a sample of 315 feet with HV deformity. The influence of the shape of this joint on the values of HVA and IMA was explored. The relation between the position of the tibial sesamoid and the size of HVA and IMA as well as the dynamics of the development of this deformity depending on the shape of the first MTC joint, was examined.Results:The oblique shape of the first MTC joint was found in 165 (52.4%) feet, the transverse in 145 (46%), and the convex shape was registered in five feet (1.6%). In the oblique shape of this joint, a moderate and severe degree of HV deformity is predominant, while in the transverse shape a mild degree dominates. A statistically significant dependence of HVA on the shape of the first MTC joint was found (Sig. = 0.010), while the dependence of IMA did not show statistical significance (Sig. = 0.105). HVA values follow the position of the tibial sesamoid in both shapes of the MTC joint while the size of the IMA in the transverse shape is not consistent with the position of this sesamoid.Conclusion:The oblique shape of the first MTC joint is associated with the more severe form of HV deformity and its faster developmental course. In the analyzed sample, it was shown that HVA is higher in the oblique shape of the MTC joint and significantly depends on the anatomical orientation of this joint. Furthermore, IMA has a higher value in the oblique shape compared to transverse but this dependence is not statistically significant. The analysis showed that the oblique shape of the first MTC joint contributes to the development of HV deformity.