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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Discovering Ca II absorption lines with a neural network

Quasar absorption line analysis is critical for studying gas and dust components and their physical and chemical properties as well as the evolution and formation of galaxies in the early universe. Calcium II (Ca II ) absorbers, which are one of the dustiest absorbers and are located at lower redshifts than most other absorbers, are especially valuable when studying physical processes and conditions in recent galaxies. However, the number of known quasar Ca II absorbers is relatively low due to the difficulty of detecting them with traditional methods. In this work, we developed an accurate and quick approach to search for Ca II absorption lines using deep learning. In our deep learning model, a convolutional neural network, tuned using simulated data, is used for the classification task. The simulated training data are generated by inserting artificial Ca II absorption lines into original quasar spectra from the Sloan Digital Sky Survey (SDSS), while an existing Ca II catalogue is adopted as the test set. The resulting model achieves an accuracy of 96 per cent on the real data in the test set. Our solution runs thousands of times faster than traditional methods, taking a fraction of a second to analyse thousands of quasars, while traditional methods may take days to weeks. The trained neural network is applied to quasar spectra from SDSS’s DR7 and DR12 and discovered 399 new quasar Ca II absorbers. In addition, we confirmed 409 known quasar Ca II absorbers identified previously by other research groups through traditional methods.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Aspartate Residues in a Forisome-Forming SEO Protein Are Critical for Protein Body Assembly and Ca 2+ Responsiveness

Forisomes are protein bodies known exclusively from sieve elements of legumes. Forisomes contribute to the regulation of phloem transport due to their unique Ca 2+ -controlled, reversible swelling. The assembly of forisomes from sieve element occlusion (SEO) protein monomers in developing sieve elements and the mechanism(s) of Ca 2+ -dependent forisome contractility are poorly understood because the amino acid sequences of SEO proteins lack conventional protein–protein interaction and Ca 2+ -binding motifs. Here we selected amino acids potentially responsible for forisome-specific functions by analyzing SEO protein sequences in comparison to those of the widely distributed SEO-related (SEOR), or SEOR proteins. SEOR proteins resemble SEO proteins closely but lack any Ca 2+ responsiveness. We exchanged identified candidate residues by directed mutagenesis of the Medicago truncatula SEO1 gene, expressed the mutated genes in yeast ( Saccharomyces cerevisiae ) and studied the structural and functional phenotypes of the forisome-like bodies that formed in the transgenic cells. We identified three aspartate residues critical for Ca 2+ responsiveness and two more that were required for forisome-like bodies to assemble. The phenotypes observed further suggested that Ca 2+ -controlled and pH-inducible swelling effects in forisome-like bodies proceeded by different yet interacting mechanisms. Finally, we observed a previously unknown surface striation in native forisomes and in recombinant forisome-like bodies that could serve as an indicator of successful forisome assembly. To conclude, this study defines a promising path to the elucidation of the so-far elusive molecular mechanisms of forisome assembly and Ca 2+ -dependent contractility.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Compositional evidence for chondrule origins of low‐Ca pyroxenes in comet Wild 2 and a giant cluster IDP

Abstract A literature compilation of 1136 low‐Ca pyroxene compositions from chondrules from 12 primitive type 2–3 carbonaceous, ordinary and enstatite chondrite groups define unique regions on an Al 2 O 3 and Cr 2 O 3 diagram when compared to low‐Ca pyroxenes from equilibrated type 4‐6 chondrites. Measured compositions of 100 low‐Ca pyroxenes from comet Wild 2 and a giant cluster IDP of probable cometary origin are similar to each other and fall in the type 2–3 chondrite chondrule region suggesting that most of the pyroxenes likely formed in the solar nebula like conventional chondrules. The data imply that most low Ca‐pyroxenes from comet Wild 2 and the giant cluster IDP formed from igneous crystallization processes and did not experience significant thermal metamorphism, indicating that the low‐Ca pyroxenes were unlikely incorporated into large parent bodies prior to accretion in their respective comet bodies. An intriguing group of nine low‐Ca pyroxenes from comet Wild 2 with low Cr and Al that fall where type 4–6 chondrites are located are interpreted as products of condensation. The compositional data combined with previously measured oxygen isotopes on 17 low‐Ca pyroxenes support earlier conclusions that comet samples have links with carbonaceous, ordinary, and possibly enstatite chondrite groups. Our results provide additional evidence that comets accreted materials from multiple chondrule reservoirs throughout the solar nebula.

Geochemistry & Geophysics↗
DOE OSTI2022

Foliar Spraying of Solanum tuberosum L. with CaCl2 and Ca(NO3)2: Interactions with Nutrients Accumulation in Tubers

Calcium is essential for plants, yet as its mobility is limited, the understanding of the rate of Ca2+ accumulation and deposition in tissues of tubers, as well as the interactions with other critical nutrients prompted this study. To assess the interactions and differential accumulation of micro and macronutrients in the tissues of tubers, Solanum tuberosum L. varieties Agria and Rossi were cultivated and, after the beginning of tuberization, four foliar sprayings (at 8–10 day intervals) with CaCl2 (3 and 6 kg ha−1) or Ca(NO3)2 (2 and 4 kg ha−1) solutions were performed. It was found that both fertilizers increased Ca accumulation in tubers (mostly in the parenchyma tissues located in the center of the equatorial region). The functioning of the photosynthetic apparatus was not affected until the 3rd application but was somewhat affected when approaching the end of the crop cycle (after the 4th application), although the lower dose of CaCl2 seemed to improve the photochemical use of energy, particularly when compared with the greater dose of Ca(NO3)2. Still, none of these impacts modified tuber height and diameter. Following the increased accumulation of Ca, in the tubers of both varieties, the mean contents of P, K, Na, Fe, and Zn revealed different accumulation patterns. Moreover, accumulation of K, Fe, Mn, and Zn prevailed in the epidermis, displaying a contrasting pattern relative to Ca. Therefore, Ca accumulation revealed a heterogeneous trend in the different regions analyzed, and Ca enrichment of tubers altered the accumulation of other nutrients.

Coelho, Ana Rita F. (ORCID:0000000339447240)↗
DOE OSTI2020

Materials Data on Ca(ZnGe)2 by Materials Project

Ca(ZnGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Zn and eight equivalent Ge atoms. All Ca–Zn bond lengths are 3.44 Å. All Ca–Ge bond lengths are 3.31 Å. Zn is bonded to four equivalent Ca and four equivalent Ge atoms to form a mixture of distorted edge, face, and corner-sharing ZnCa4Ge4 tetrahedra. All Zn–Ge bond lengths are 2.58 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Zn, and one Ge atom. The Ge–Ge bond length is 2.51 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(BIr)2 by Materials Project

Ca(IrB)2 is alpha Pu-derived structured and crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Ca is bonded in a 10-coordinate geometry to eight equivalent Ir and six equivalent B atoms. There are four shorter (3.05 Å) and four longer (3.29 Å) Ca–Ir bond lengths. There are two shorter (3.00 Å) and four longer (3.15 Å) Ca–B bond lengths. Ir is bonded in a 4-coordinate geometry to four equivalent Ca and four equivalent B atoms. There are two shorter (2.09 Å) and two longer (2.16 Å) Ir–B bond lengths. B is bonded in a 4-coordinate geometry to three equivalent Ca and four equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(As2Rh3)2 by Materials Project

Ca(Rh3As2)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ca is bonded to six equivalent Rh and six equivalent As atoms to form face-sharing CaAs6Rh6 cuboctahedra. All Ca–Rh bond lengths are 3.16 Å. All Ca–As bond lengths are 3.06 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 6-coordinate geometry to two equivalent Ca and four As atoms. There are two shorter (2.46 Å) and two longer (2.55 Å) Rh–As bond lengths. In the second Rh site, Rh is bonded in a 5-coordinate geometry to five As atoms. There are one shorter (2.55 Å) and four longer (2.59 Å) Rh–As bond lengths. There are two inequivalent As sites. In the first As site, As is bonded in a 8-coordinate geometry to two equivalent Ca and six Rh atoms. In the second As site, As is bonded in a 9-coordinate geometry to nine Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(GeIr)2 by Materials Project

Ca(IrGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent Ge atoms. All Ca–Ir bond lengths are 3.35 Å. All Ca–Ge bond lengths are 3.24 Å. Ir is bonded in a 4-coordinate geometry to four equivalent Ca and four equivalent Ge atoms. All Ir–Ge bond lengths are 2.47 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Ir, and one Ge atom. The Ge–Ge bond length is 2.61 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(GePd)2 by Materials Project

Ca(PdGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Pd and eight equivalent Ge atoms. All Ca–Pd bond lengths are 3.35 Å. All Ca–Ge bond lengths are 3.34 Å. Pd is bonded in a 4-coordinate geometry to four equivalent Ca and four equivalent Ge atoms. All Pd–Ge bond lengths are 2.53 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Pd, and one Ge atom. The Ge–Ge bond length is 2.53 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(GeRu)2 by Materials Project

Ca(RuGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Ru and eight equivalent Ge atoms. All Ca–Ru bond lengths are 3.30 Å. All Ca–Ge bond lengths are 3.31 Å. Ru is bonded in a 4-coordinate geometry to four equivalent Ca and four equivalent Ge atoms. All Ru–Ge bond lengths are 2.45 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Ru, and one Ge atom. The Ge–Ge bond length is 2.67 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(NiGe)2 by Materials Project

Ca(NiGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Ni and eight equivalent Ge atoms. All Ca–Ni bond lengths are 3.23 Å. All Ca–Ge bond lengths are 3.18 Å. Ni is bonded in a 4-coordinate geometry to four equivalent Ca and four equivalent Ge atoms. All Ni–Ge bond lengths are 2.37 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Ni, and one Ge atom. The Ge–Ge bond length is 2.63 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(CoGe)2 by Materials Project

Ca(CoGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Co and eight equivalent Ge atoms. All Ca–Co bond lengths are 3.27 Å. All Ca–Ge bond lengths are 3.13 Å. Co is bonded to four equivalent Ca and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing CoCa4Ge4 tetrahedra. All Co–Ge bond lengths are 2.34 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Co, and one Ge atom. The Ge–Ge bond length is 2.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(CuGe)2 by Materials Project

Ca(CuGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Cu and eight equivalent Ge atoms. All Ca–Cu bond lengths are 3.30 Å. All Ca–Ge bond lengths are 3.19 Å. Cu is bonded in a 4-coordinate geometry to four equivalent Ca and four equivalent Ge atoms. All Cu–Ge bond lengths are 2.46 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Cu, and one Ge atom. The Ge–Ge bond length is 2.50 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(ClO3)2 by Materials Project

Ca(ClO3)2 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ca–O bond distances ranging from 2.49–2.62 Å. There are three inequivalent O sites. In the first O site, O is bonded in a trigonal planar geometry to two equivalent Ca and one Cl atom. The O–Cl bond length is 1.53 Å. In the second O site, O is bonded in a bent 150 degrees geometry to one Ca and one Cl atom. The O–Cl bond length is 1.49 Å. In the third O site, O is bonded in a distorted bent 120 degrees geometry to one Ca and one Cl atom. The O–Cl bond length is 1.50 Å. Cl is bonded in a trigonal non-coplanar geometry to three O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(ClO3)2 by Materials Project

Ca(ClO3)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ca is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of Ca–O bond distances ranging from 2.57–2.83 Å. There are three inequivalent O sites. In the first O site, O is bonded in a distorted trigonal planar geometry to two equivalent Ca and one Cl atom. The O–Cl bond length is 1.52 Å. In the second O site, O is bonded in a bent 120 degrees geometry to one Ca and one Cl atom. The O–Cl bond length is 1.49 Å. In the third O site, O is bonded in a 3-coordinate geometry to two equivalent Ca and one Cl atom. The O–Cl bond length is 1.52 Å. Cl is bonded in a trigonal non-coplanar geometry to three O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(AgGe)2 by Materials Project

Ca(AgGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Ag and eight equivalent Ge atoms. All Ca–Ag bond lengths are 3.52 Å. All Ca–Ge bond lengths are 3.33 Å. Ag is bonded in a 12-coordinate geometry to four equivalent Ca, four equivalent Ag, and four equivalent Ge atoms. All Ag–Ag bond lengths are 3.10 Å. All Ag–Ge bond lengths are 2.67 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Ag, and one Ge atom. The Ge–Ge bond length is 2.43 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(GeAu)2 by Materials Project

Ca(AuGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Au and eight equivalent Ge atoms. All Ca–Au bond lengths are 3.45 Å. All Ca–Ge bond lengths are 3.43 Å. Au is bonded in a 4-coordinate geometry to four equivalent Ca and four equivalent Ge atoms. All Au–Ge bond lengths are 2.64 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ca, four equivalent Au, and one Ge atom. The Ge–Ge bond length is 2.48 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(AlGa)2 by Materials Project

Ca(GaAl)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca is bonded in a 8-coordinate geometry to eight equivalent Ga and eight equivalent Al atoms. All Ca–Ga bond lengths are 3.28 Å. All Ca–Al bond lengths are 3.49 Å. Ga is bonded in a 9-coordinate geometry to four equivalent Ca, one Ga, and four equivalent Al atoms. The Ga–Ga bond length is 2.49 Å. All Ga–Al bond lengths are 2.62 Å. Al is bonded to four equivalent Ca and four equivalent Ga atoms to form a mixture of distorted edge, face, and corner-sharing AlCa4Ga4 tetrahedra.

36 MATERIALS SCIENCE↗