Significant volumes of waste rock are produced in mining operations, particularly in open pit operations. Waste rock is characterized by a high heterogeneity in their mineralogical, hydrogeological, ...and physical properties, especially in comparison to tailings. The purpose of this study was to develop an improved method to quantify the net acid-generating potential of waste rock by incorporating the degree of liberation of acid-generating and neutralizing minerals. Three lithologies were sampled immediately after waste rock blasting. Each lithology was separated into seven fractions: D < 0.053 mm, 0.053 mm < D < 0.3 mm, 0.3 mm < D < 0.85 mm, 0.85 mm < D < 2.4 mm, 2.4 mm < D < 5 mm, 5 mm < D < 15 mm, 15 mm < D < 50 mm; particles >5 cm were not considered. Mineralogical and chemical characterizations showed that sulphides, mainly pyrite, were enriched in the fine to mid-sized fractions (between 0.053 mm and 0.85 mm), and carbonates, mainly calcite, decreased as the particle size increased. Sulphides were more liberated within the fine fractions and their liberation was considered negligible at sizes >2.4 mm. For coarser fractions (>5 mm), sulphides were associated with non-sulphide gangue minerals which was confirmed by micro-computed tomography. The waste rock samples were submitted to both acid base accounting (ABA) and net acid generation (NAG) tests to evaluate their acid-generating potentials. Sixteen size fractions were non-acid generating and five were classified as uncertain. However, standard ABA and NAG tests are based on pulverized samples that don't consider the initial textures of samples. Therefore, ABA results (acid-generating potentials and neutralization potentials) were corrected using the degrees of sulphide and carbonate liberation. The corrected classifications reduced the acid-generating potential of most of the uncertain samples due to the high carbonates content in relation to sulphides. This study also defines a parameter, the diameter of physical locking of sulphides, that can be used to separate waste rock into a reactive and non-reactive fraction based on the relationship between sulphide liberation and particle-size fraction. The reactive fraction refers to waste rock likely to require active acid rock drainage (ARD) management, whereas non-reactive fraction refers to waste rock likely not require active management.
•Sulphides are mainly enriched in the fine to mid-sized fraction.•Sulphides were more liberated within the fine fractions and their liberation was negligible at size >2.4 mm.•Sulphide and carbonate liberations are used to correct AP and NP of pulverized samples to consider the initial texture of samples.•Diameter of physical locking of sulphides separates a waste rock into two fractions with different reactivities.
Whether supernovae are major sources of dust in galaxies is a long-standing debate. We present infrared and submillimeter photometry and spectroscopy from the Herschel Space Observatory of the Crab ...Nebula between 51 and 670 mu m as part of the Mass Loss from Evolved StarS program. We compare the emission detected with Herschel with multiwavelength data including millimeter, radio, mid-infrared, and archive optical images. We carefully remove the synchrotron component using the Herschel and Planck fluxes measured in the same epoch. The contribution from line emission is removed using Herschel spectroscopy combined with Infrared Space Observatory archive data. Several forbidden lines of carbon, oxygen, and nitrogen are detected where multiple velocity components are resolved, deduced to be from the nitrogen-depleted, carbon-rich ejecta. No spectral lines are detected in the SPIRE wavebands; in the PACS bands, the line contribution is 5% and 10% at 70 and 100 mu m and negligible at 160 mu m. After subtracting the synchrotron and line emission, the remaining far-infrared continuum can be fit with two dust components. Assuming standard interstellar silicates, the mass of the cooler component is 0.24 super(+0.32) sub(-0.08) M sub(middot in circle) for T = 28.1 super(+5.5) sub(-3.2) K. Amorphous carbon grains require 0.11 + or - 0.01 M sub(middot in circle) of dust with T = 33.8 super(+2.3) sub(-1.8) K. A single temperature modified blackbody with 0.14 M sub(middot in circle) and 0.08 M sub(middot in circle) for silicate and carbon dust, respectively, provides an adequate fit to the far-infrared region of the spectral energy distribution but is a poor fit at 24-500 mu m. The Crab Nebula has condensed most of the relevant refractory elements into dust, suggesting the formation of dust in core-collapse supernova ejecta is efficient.
A
bstract
We propose worldsheet formulae for wavefunction coefficients of the massive non-linear sigma model (NLSM), scalar Dirac-Born-Infeld (DBI), and special Galileon (sGal) theories in de Sitter ...momentum space in terms of the recently proposed cosmological scattering equations constructed from conformal generators in the future boundary. The four-point integrands are assembled from simple building blocks and we identify a double copy prescription mapping the NLSM wavefunction coefficient to the DBI and sGal wavefunction coefficients, including mass deformations and curvature corrections. Finally, we compute the soft limits of these wavefunction coefficients and find that they can be written in terms of boundary conformal generators acting on contact diagrams.
Theoretical models predict that core-collapse supernovae (CCSNe) can be efficient dust producers (0.1-1.0 M...), potentially accounting for most of the dust production in the early Universe. ...Observational evidence for this dust production efficiency is however currently limited to only a few CCSN remnants (e.g. SN 1987A, Crab nebula). In this paper, we revisit the dust mass produced in Cassiopeia A (Cas A), a ~330-yr old O-rich Galactic supernova remnant (SNR) embedded in a dense interstellar foreground and background. We present the first spatially resolved analysis of Cas A based on Spitzer and Herschel infrared and submillimetre data at a common resolution of ~0.6 arcmin for this 5 arcmin diameter remnant following a careful removal of contaminating line emission and synchrotron radiation. We fit the dust continuum from 17 to 500 ...m with a four-component interstellar medium and supernova (SN) dust model. We find a concentration of cold dust in the unshocked ejecta of Cas A and derive a mass of 0.3-0.5 M... of silicate grains freshly produced in the SNR, with a lower limit of greater than or equal to 0.1-0.2 M... For a mixture of 50 per cent of silicate-type grains and 50 per cent of carbonaceous grains, we derive a total SN dust mass between 0.4 and 0.6 M... These dust mass estimates are higher than from most previous studies of Cas A and support the scenario of SN-dominated dust production at high redshifts. We furthermore derive an interstellar extinction map for the field around Cas A which towards Cas A gives average values of A sub( V) = 6-8 mag, up to a maximum of A sub( V) = 15 mag. (ProQuest: ... denotes formulae/symbols omitted.)
ABSTRACT
We present a self-consistent cross-calibration of the three main molecular gas mass tracers in galaxies, namely the 12CO(1–0), C i(3P1–3P0) lines, and the submm dust continuum emission, ...using a sample of 407 galaxies, ranging from local discs to submillimetre-selected galaxies (SMGs) up to z ≈ 6. A Bayesian statistical method is used to produce galaxy-scale universal calibrations of these molecular gas indicators, that hold over 3–4 orders of magnitude in infrared luminosity, LIR. Regarding the dust continuum, we use a mass-weighted dust temperature, Tmw, determined using new empirical relations between temperature and luminosity. We find the average L/Mmol gas mass conversion factors (including He) to be ${\alpha _{850}}=6.9\times 10^{12}\, \rm W\, Hz^{-1}\, M_{\odot }^{-1}$, αCO = 4.0 M⊙ (κ km s−1 pc2)−1, and $\alpha _{\rm C\, I}$ = 17.0 M⊙ (κ km s−1 pc2)−1, based on the assumption that the mean dust properties of the sample (κH = gas-to-dust ratio/dust emissivity) will be similar to those of local metal rich galaxies and the Milky Way. The tracer with the least intrinsic scatter is C i(1–0), while CO(1–0) has the highest. The conversion factors show a weak but significant correlation with LIR which is not apparent when Tmw is held constant. Assuming dust properties typical of metal-rich galaxies, we infer a neutral carbon abundance ${X_{\rm C\, I}}=\rm C^0/\rm{H_2}=1.6\times 10^{-5}$, similar to that in the Milky Way. We find no evidence for bi-modality of αCO between main-sequence (MS) galaxies and those with extreme star-formation intensity, i.e. ultraluminous infrared galaxies (ULIRGs) and SMGs. The means of the three conversion factors are found to be similar between MS galaxies and ULIRGs/SMGs, to within 10–20 per cent. The overarching conclusion of our work is that, for metal-rich galaxies, near-universal average values for αCO, $X_{\rm C\, I}$, and κH are adequate for global molecular gas estimates within the expected uncertainties. The 1σ scatter in our optimized values for αCO, $X_{\rm C\, I}$, and κH are 0.14, 0.11, and 0.15 dex, respectively.
ABSTRACT
We build a rigorous statistical framework to provide constraints on the chemical and dust evolution parameters for nearby late-type galaxies with a wide range of gas fractions ($3{{\ \rm ...per\ cent}}\lt f_g\lt 94{{\ \rm per\ cent}}$). A Bayesian Monte Carlo Markov Chain framework provides statistical constraints on the parameters used in chemical evolution models. Nearly a million one-zone chemical and dust evolution models were compared to 340 galaxies. Relative probabilities were calculated from the χ2 between data and models, marginalized over the different time-steps, galaxy masses, and star formation histories. We applied this method to find ‘best-fitting’ model parameters related to metallicity, and subsequently fix these metal parameters to study the dust parameters. For the metal parameters, a degeneracy was found between the choice of initial mass function, supernova metal yield tables, and outflow prescription. For the dust parameters, the uncertainties on the best-fitting values are often large except for the fraction of metals available for grain growth, which is well constrained. We find a number of degeneracies between the dust parameters, limiting our ability to discriminate between chemical models using observations only. For example, we show that the low dust content of low-metallicity galaxies can be resolved by either reducing the supernova dust yields and/or including photofragmentation. We also show that supernova dust dominates the dust mass for low-metallicity galaxies and grain growth dominates for high-metallicity galaxies. The transition occurs around 12 + log (O/H) = 7.75, which is lower than found in most studies in the literature.
In bananas, the major carotenoids are α- and β-carotene, which give this fruit great potential in biofortification programs. The carotenoid content in pulp and peel of 22 banana and plantain ...genotypes was determined in order to evaluate the impact of ripening on the carotenoid content as well as its retention after different thermal processes. Fruits were ripened at stage 2 (green), 5 (yellow) and 7 (yellow with dark spots). The provitamin A content (pVACs) varied from 20.8 (‘Muisa Tia’ stg 7) to 6341.5 μg/100 g f.w. (‘Samurá B’ stg 5). High quantities were identified in plantains, which have yellow pulp, a phenotypic characteristic that can indicate the quantity of pVACs in Musa spp. fruit. The ‘Samurá B’ plantain showed the highest pVACs (6341.5 μg/100 g f.w.) and trans-β-carotene (5220.0 μg/100 g f.w.) content in pulp, especially when compared to the ‘D'Angola’ plantain (pVACs: 3214.0 μg/100 g f.w.), the most common in Brazil, and with the dessert cultivar from the Cavendish subgroup (‘Grand Naine’ – pVACs: 230.6 μg/100 g f.w.), the most consumed worldwide. The highest pVACs quantity was verified in the ripe fruit (stg 5), decreasing during the fruit ripening (stg 7). In the peels, lutein was the majority compost, with contents higher than the pulp. The highest lutein content was identified in the green fruit peels from the ‘Terra Anã Branca’ cultivar (1602.1 μg/100 g d.w.), almost ten times higher than the content found in the pulp of the same cultivar. However, the pulp of all the cultivars showed superior values of pVACs, trans-β-carotene and trans-α-carotene, mainly in the ripe stage 5. The plantain ‘Samurá B’ has nutritional and/or functional properties, and its promotion/incorporation in existing agricultural systems is of interest for use in biofortification programs. In addition, thermal processing can improve bioactive compounds release and increase the functional and nutritional value of the Musa spp. fruit, mainly by boiling, which should be the favorite in domestic preparations, regardless of the cultivar used.
Display omitted
•Twenty-two banana and plantain genotypes were analyzed.•Bananas and plantains contain as major carotenoid α and β-carotene.•Highest lutein content was found in the green fruit peel.•High levels of pro-vitamin A carotenoids occur in plantain with yellow pulp.•Boiling process improve the pro-vitamin A carotenoids release in Musa spp. fruits.
We apply a chemical evolution model to investigate the sources and evolution of dust in a sample of 26 high-redshift (z > 1) submillimetre galaxies (SMGs) from the literature, with complete ...photometry from ultraviolet to the submillimetre. We show that dust produced only by low–intermediate-mass stars falls a factor 240 short of the observed dust masses of SMGs, the well-known ‘dust-budget crisis’. Adding an extra source of dust from supernovae can account for the dust mass in 19 per cent of the SMG sample. Even after accounting for dust produced by supernovae the remaining deficit in the dust mass budget provides support for higher supernova yields, substantial grain growth in the interstellar medium or a top-heavy IMF. Including efficient destruction of dust by supernova shocks increases the tension between our model and observed SMG dust masses. The models which best reproduce the physical properties of SMGs have a rapid build-up of dust from both stellar and interstellar sources and minimal dust destruction. Alternatively, invoking a top-heavy IMF or significant changes in the dust grain properties can solve the dust budget crisis only if dust is produced by both low-mass stars and supernovae and is not efficiently destroyed by supernova shocks.
Display omitted
•Plantains and cooking bananas presented a high content of resistant starch.•Peel showed superior phenolic compounds and minerals levels than pulp.•Ripe dessert and cooking banana ...presented high values of phenolic compounds.•Catechin and quercetin contributed strongly to the antioxidant activity of the Musa spp.•Boiling with peel increased the phenolic compounds ofMusaspp. fruit.
Genotypes of bananas and plantains have been studied for biofortification purposes, mainly due to content of resistant starch (RS) and polyphenols. This study aims to identify banana and plantain genotypes with a high content of resistant starch, phenolic compounds and minerals, and to evaluate the impact of the ripening stage and domestic thermal processing to select superior genotypes with high levels of functional compounds. In this study, it was used bunches of bananas and plantain genotypes. The phenolic compounds profiles were determined by HPLC-DAD in pulps and peels. The resistant starch and the minerals (K, Na, Zn, Cu and Fe) were evaluated in pulps and peels of unripe fruit. The results of phenolic compounds were studied in three ripening stages, and after thermal processing (ripe stage) of two genotypes, which were most promising for biofortification studies. Resistant starch and minerals were analysed in the unripe fruits. The peel biomass showed the highest values of phenolic compounds and minerals. The total starch content in the pulp varied from 42.3% (‘FC06-02′) to 80.6% (‘Pelipita’). Plantains and cooking bananas presented the highest contents of starch and resistant starch (stage 2 – green with yellow traces). The pulps of the dessert genotypes ‘Khai’ and ‘Ouro da Mata’, and cooking genotype ‘Pacha Nadam’ stood out due to their minerals high contents (P, K and Fe; Zn and Fe; Ca, Mg and Zn, respectively). The dessert bananas (e.g., ‘Ney Poovan’) and cooking bananas (e.g., ‘Tiparot’) had the highest concentrations of phenolic compounds, mainly in ripe fruit (stage 5 – yellow with green). In addition, the thermal processing of Musa spp. fruit led to increasing these secondary metabolites, mainly the cooking of fruit with peel by boiling, which should be preferred in domestic preparations.
ABSTRACT
Dust destruction by supernovae is one of the main processes removing dust from the interstellar medium (ISM). Estimates of the efficiency of this process, both theoretical and observational, ...typically assume a shock propagating into a homogeneous medium, whereas the ISM possesses significant substructure in reality. We self-consistently model the dust and gas properties of the shocked ISM in three supernova remnants (SNRs), using X-ray and infrared (IR) data combined with corresponding emission models. Collisional heating by gas with properties derived from X-ray observations produces dust temperatures too high to fit the far-IR fluxes from each SNR. An additional colder dust component is required, which has a minimum mass several orders of magnitude larger than that of the warm dust heated by the X-ray emitting gas. Dust-to-gas mass ratios indicate that the majority of the dust in the X-ray emitting material has been destroyed, while the fraction of surviving dust in the cold component is plausibly close to unity. As the cold component makes up virtually all the total dust mass, destruction time-scales based on homogeneous models, which cannot account for multiple phases of shocked gas and dust, may be significantly overestimating actual dust destruction efficiencies, and subsequently underestimating grain lifetimes.
PDF
