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Abstract Spicules, the smallest observable jetlike dynamic features ubiquitous in the chromosphere, are supposedly an important potential source for small-scale solar wind transients, with supporting evidence yet needed. We studied the high-resolution Hαimages (0.″10) and magnetograms (0.″29) from the Big Bear Solar Observatory to find that spicules are an ideal candidate for the solar wind magnetic switchbacks detected by the Parker Solar Probe (PSP). It is not that spicules are a miniature of coronal jets, but that they have unique properties not found in other solar candidates in explaining solar origin of switchbacks. (1) The spicules under this study originate from filigrees, all in a single magnetic polarity. Since filigrees are known as footpoints of open fields, the spicule guiding field lines can form a unipolar funnel, which is needed to create an SB patch, a group of field lines that switch from one common base polarity to the other polarity. (2) The spicules come in a cluster lined up along a supergranulation boundary, and the simulated waiting times from their spatial intervals exhibit a number distribution continuously decreasing from a few seconds to ∼30 minutes, similar to that of switchbacks. (3) From a time–distance map for spicules, we estimate their occurrence rate as 0.55 spicules Mm−2s−1, which is sufficiently high for detection by PSP. In addition, the dissimilarity of spicules with coronal jets, including the absence of base brightening and low correlation with EUV emission, is briefly discussed.
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On stars and spikes: Resolving the skeletal morphology of planktonic Acantharia using synchrotron X-ray nanotomography and deep learning image segmentation
Acantharia ( Acantharea ) are wide-spread marine protozoa, presenting one of the rare examples of stron- tium sulfate mineralization in the biosphere. Their endoskeletons consist of 20 spicules arranged accord- ing to a unique geometric pattern named Müller’s principle. Given the diverse mineral architecture of the Acantharia class, we set out to examine the complex three-dimensional skeletal morphology at the nanometer scale using synchrotron X-ray nanotomography, followed by image segmentation based on deep learning methods. The present study focuses on how the spicules emanate from the robust central junction in the orders Symphyacanthida and Arthracanthida , the geometry of lateral spicule wings as well as pockets of interspicular space, which may be involved in cell compartmentalization. Through these morphometric studies, we observed subtle deviations from the previously described spatial arrangement of the spicules. According to our data, spicule shapes are adjusted in opposite spicules as to accommodate the overall spicule arrangement. In all types examined, previously unknown interspicular interstices were found in areas where radial spicules meet, which could have implications for the crystal growth mecha- nism and overall endoskeletal integrity. A deeper understanding of the spiculogenesis in Acantharia can provide biomimetic routes towards complex inorganic shapes.
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- Award ID(s):
- 2137663
- PAR ID:
- 10481821
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Acta Biomaterialia
- Volume:
- 159
- Issue:
- C
- ISSN:
- 1742-7061
- Page Range / eLocation ID:
- 74 to 82
- Subject(s) / Keyword(s):
- Biomineralization Crystallization X-ray nanotomography Deep learning image segmentation Strontium sulfate Biomaterials Biointerface Morphogenesis
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.actbio.2023.01.037
