This work investigates the recycling of sugarcane bagasse ash waste as a method to provide raw material for clay brick bodies, through replacement of natural clay by up 20 wt.%. Initially, the waste ...sample was characterized by its chemical composition, X-ray diffraction, differential thermal analysis, particle size, morphology and pollution potential. Clay bricks pieces were prepared, and then tested, so as to determine their technological properties (e.g., linear shrinkage, water absorption, apparent density, and tensile strength). The sintered microstructure was evaluated by scanning electron microscopy (SEM). It was found that the sugarcane bagasse ash waste is mainly composed by crystalline silica particles. The test results indicate that the sugarcane bagasse ash waste could be used as a filler in clay bricks, thus enhancing the possibility of its reuse in a safe and sustainable way.
► A new alternative for the recycling of sugarcane bagasse ash waste is needed. ► Sugarcane bagasse ash waste as raw material for clay bricks. ► Sugarcane bagasse ash waste contains crystalline quartz as the major component. ► Sugarcane bagasse ash influences the properties and microstructure of clay bricks.
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ABSTRACT
In this work, we show that TYC 8327-1678-1 is a low-mass red giant star with a super lithium abundance in its atmosphere. For this, we used high-resolution spectroscopy to determine ...atmospheric parameters, the chemical abundances of the light elements and the isotopic ratio 12C/13C using the spectral synthesis techniques and the equivalent width measurements. Also, we used theoretical evolutionary tracks to find out the mass and the evolutionary stage of TYC 8327-1678-1. The lithium abundance was determined using the Li i resonance doublet at 6708 Å and the subordinate line at 6104 Å that yielding a mean value of $\log \, \epsilon {\rm (Li)_{NLTE}}\, =\, 3.48$. The projected rotational velocity ($v\, \sin \, i$) has been determined using spectral synthesis based on the isolated Fe i lines. Our results show that TYC 8327-1678-1 has a mass of $M\, =\, 1.60$ $\pm \, 0.20\, {\rm M}_{\odot }$, a low rotational velocity ($v\, \sin \, i$ = 2.35 ± 0.24 km s−1) and metallicity of Fe/H = +0.23 ± 0.09. Finally, we discuss the possibility that TYC 8327-1678-1 became a lithium-rich star after a merging event involving a red giant and a helium white dwarf.
Abstract A classical local thermodynamic equilibrium analysis, based on high-resolution spectroscopic data, is performed for a sample of three potential barium dwarf candidates and one star already ...recognized as such. We derived their atmospheric parameters, estimated their masses and luminosities, and determined chemical abundances for a set of 21 elements, including CNO. Some elemental abundances are derived for the first time in HD 15096, HD 37792, and HD 141804. The program stars are dwarfs/subgiants with metallicities typical of disk stars, exhibiting moderate carbon enhancements, with C/Fe ratios ranging from +0.29 to +0.66 dex, and high levels of slow neutron-capture ( s -process) elements, with s /Fe ≳ + 1.0 dex. As spectroscopic binaries, their peculiarities are attributable to mass transfer events. The observed neutron-capture patterns of were individually compared with two sets of s -process nucleosynthesis models (Monash and fruity ), yielding dilution factors and masses estimates for the former polluting asymptotic giant branch stars. Low-mass (≲3.0 M ⊙ ) models successfully reproduce the observations. In addition, we estimated mean neutron exposures on the order of 0.6–0.7 mb −1 for the s -processed material observed in their envelopes. Applying an empirical initial-final mass relation, we constraint in ∼0.7 M ⊙ the mass of their dim white dwarf companions. Moreover, our kinematic study revealed that the program stars are members of the thin disk, with probabilities greater than 70%. Hence, we identified HD 15096 and HD 37792 as new barium dwarfs and confirmed that HD 141804 is a barium dwarf. Thus, the number of barium dwarfs identified in the literature from high-resolution spectroscopy increases to 71 objects.
Abstract
We report the discovery of a lithium-rich giant, HD 150382, a post-red-giant-branch clump star. The atmospheric parameters, the chemical abundances for 17 elements, and the isotopic ratio
12
...C/
13
C were determined using the equivalent width and the spectral synthesis methods. The lithium abundance was determined via spectral synthesis of the Li
i
resonance doublet at
λ
6708 yielding log
ϵ
(Li)
NLTE
= 2.55. The excited-state line at
λ
6104 also was analyzed. In addition, we have used theoretical evolutionary tracks to determine the mass and luminosity of HD 150382 and compare it with other well-known lithium-rich giants in the literature. Our results show that HD 150382 is a slowly rotating K-giant star having near-solar metallicity. We also show that HD 150382 is not s-process enriched, which is in agreement with its evolutionary status. Finally, based on the abundance results, we study the possible scenarios of the lithium enrichment.
Abstract
Sodium-rich stars are often found in globular clusters giants. However, some sodium-rich stars have been found among field metal-poor stars. These stars are considered as evaporated from ...globular clusters. Identified such kind of stars among the field stars in the Galaxy may provide insights of which mechanism was responsible for the ejection from a globular cluster and may reveal some chemical peculiarity. Therefore, we started a search, using high-resolution spectroscopy, among metal-poor stars from several sources of the literature to find a sodium-rich star. Here we present the results for the temperature, gravity, metallicity, and sodium abundances for the stars of our sample. For many of them we determined the temperature, gravity, metallicity, and sodium abundances for the first time. As a result of our search we found one star, CD-23°16310, which has a Na/Fe ratio of +1.09. We also show that CD-23°16310 is not a carbon-enhanced metal-poor (CEMP) star since carbon is not enriched but is nitrogen-rich. We did not detect any variation of the radial velocity that would support the hypothesis of mass transfer. Thus, the high sodium and nitrogen abundance could be due to a strong internal mixing process, suggesting that CD-23°16310 is an early asymptotic giant branch star.
In this paper, we quantize superconformal σ models defined by worldline supermultiplets. Two types of superconformal mechanics, with and without a De Alfaro Fubini Furlan (DFF) term, are considered. ...Without a DFF term (Calogero potential only), the supersymmetry is unbroken. The models with a DFF term correspond to deformed (if the Calogero potential is present) or undeformed oscillators. For these (un)deformed oscillators, the classical invariant superconformal algebra acts as a spectrum-generating algebra of the quantum theory. Besides the osp(1|2) examples, we explicitly quantize the superconformally invariant worldline σ models defined by the N=4 (1, 4, 3) supermultiplet with D(2,1;α) invariance, for α≠0,−1 and by the N=2 (2, 2, 0) supermultiplet with two-dimensional target and sl(2|1) invariance. The parameter α is the scaling dimension of the (1, 4, 3) supermultiplet and, in the DFF case, has a direct interpretation as a vacuum energy. In the DFF case, for the sl(2|1) models, the scaling dimension λ is quantized (either λ=12+Z or λ=Z). The ordinary two-dimensional oscillator is recovered, after imposing a superselection restriction, from the λ=−12 model. In particular, a single bosonic vacuum is selected. The spectrum of the unrestricted two-dimensional theory is decomposed into an infinite set of lowest-weight representations of sl(2|1). Extra fermionic raising operators, not belonging to the original sl(2|1) superalgebra, allow (for λ=12+Z) to construct the whole spectrum from the two degenerate (one bosonic and one fermionic) vacua.
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We develop a supervised machine learning algorithm that is able to learn topological phases of finite condensed-matter systems from bulk data in real lattice space. The algorithm employs ...diagonalization in real space together with any supervised learning algorithm to learn topological phases through an eigenvector ensembling procedure. We combine our algorithm with decision trees and random forests to successfully recover topological phase diagrams of Su-Schrieffer-Heeger (SSH) models from bulk lattice data in real space and show how the Shannon information entropy of ensembles of lattice eigenvectors can be used to retrieve a signal detailing how topological information is distributed in the bulk. We further use insights obtained from these information entropy signatures to engineer global topological features from real-space lattice data that still carry most of the topological information in the lattice, while greatly diminishing the size of feature space, thus effectively amounting to a topological lattice compression. Finally, we explore the theoretical possibility of interpreting the information entropy topological signatures in terms of emergent information entropy wave functions, which lead us to Heisenberg and Hirschman uncertainty relations for topological phase transitions. The discovery of Shannon information entropy signals associated with topological phase transitions from the analysis of data from several thousand SSH systems illustrates how model explainability in machine learning can advance the research of exotic quantum materials with properties that may power future technological applications such as qubit engineering for quantum computing.
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This investigation focuses on the reuse of grits waste as a raw material for replacing Portland cement by up to 30 wt.% in soil–cement bricks. The grits waste was obtained from a cellulose factory ...located in south-eastern Brazil. We initially characterized the waste sample with respect to its chemical composition, X-ray diffraction, fineness index, morphology, pozzolanic activity, and pollution potential. Soil–cement bricks were then prepared using the waste material and were tested to determine their technological properties (e.g., water absorption, apparent density, volumetric shrinkage, and compressive strength). Microstructural evolution was accompanied by confocal microscopy. It was found that the grits waste is mainly composed of calcite (CaCO3) particles. Our results indicate that grits waste can be used economically, safely, and sustainably at weight percentages of up to 20% to partially replace Portland cement in soil–cement bricks.
•Grits can be classified as a non-inert waste material.•Grits waste as raw material for soil–cement brick was studied.•Grits waste contains calcite as the major component.•Grits waste influences the technological properties of soil–cement brick.
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