Environmental consequences associated with ash-stabilisation of organic sludges from the synthol process

Includes bibliographical references.Worldwide increases in environmental awareness have led to the development of new innovative technologies aimed at site remediation and hazardous waste treatment. Solidification/Stabilisation (S/S) is one of such technologies and it has emerged as an environmentally acceptable treatment option for hazardous waste. Initially applied to inorganic wastes, S/S is now being investigated for the treatment of organic wastes and sludges. Challenges facing this venture into the SIS of organic wastes include the lack of technical information on waste-binder interactions, the uncertainty regarding an appropriate method to evaluate the performance of CPS systems, as well as evaluation of the long-term stability of stabilised material. This paper attempts to expand the understanding of chemical and micro-structural waste-binder interactions. Also addressed is the weathering behaviour of stabilised/ solidified organic waste when exposed to two different leaching media, distilled water and the US EPA's Toxicity Characteristic Leaching Procedure (TCLP) solution. Addressed to a minor extent is the effect of stabilised/solidified organic waste on biomass production of sweetcorn maize. The focus in this study was the stabilisation of the synthol sludge (synthol gunk) using a pozzolan system. This was done by preparing stabilised waste forms from synthol gunk and fine ash (ash obtained from the slimes dams, hence has hydrated to some extent). A particle size fraction less than 2 mm of these waste forms were leached with the two leaching solutions. Some of the material was pressed into pellets, which were subsequently leached in the same leaching solutions. The pellets were analysed under SEM-EDS for micro-structural analysis. In a separate set of experiments fine ash, synthol gunk and the stabilised waste forms were mixed with soil in the range 0% to 30% waste addition, after which sweetcorn maize was planted to study the effects on biomass production. Other instrumental techniques used in this study include WDXRF, ICP-MS, FTIR, IC as well as the analysis of dissolved organic carbon (DOC). The study showed that the trace metal speciation of the pozzolanic binder is affected by the presence of the organic waste, with a possible threat of turning the binder into a hazardous material. Elements that were leachable by TCLP on the stabilised product include B, Mn, Ni, Fe, and Br. The addition of lime in the system appears to lower the leachability of B, Mn, and Br while worsening the leachability of Fe, Ba, and Zn. However, addition of lime increases the leachability of B, Cr, Mn, Fe and Br in distilled water. The most likely source of B, Fe, Br and Ba is fine ash. Plant growth studies showed that the toxicity threshold of synthol gunk in the stabilised material on biomass production appears to be lowered from about 2.5% in unstabilised synthol gunk to about 1.2% either due to synergy or the additive effect of ash and synthol gunk. Furthermore, it is likely that some of the toxicity of synthol gunk is due to the hydrophobic coating of roots resulting in inadequate water intake by the plant

Exploring engineering students' epistemic beliefs and motivation: A case of a South African university

This study seeks to investigate how chemical engineering students from South African low-income communities locate knowledge structures. The study used an existing Engineering Related Beliefs Questionnaire (ERBQ) to evaluate beliefs of 268 chemical engineering students. The questionnaire collects additional information by allowing open-ended responses on each item to increase reliability of the questionnaire. Findings suggest that more than 60 per cent of students believe that engineering knowledge cannot be argued, and that learning takes place only when the lecturer transmits knowledge. Engineering educators may consider a humanizing pedagogy, which create opportunities for students from low-income communities to be liberated and reduce the dependency culture. Application of this pedagogy may assist students to achieve life long learning whilst developing necessary soft skills like independent thinking and innovation

Radio weak lensing shear measurement in the visibility domain - I. Methodology

The high sensitivity of the new generation of radio telescopes such as the Square Kilometre Array (SKA) will allow cosmological weak lensing measurements at radio wavelengths that are competitive with optical surveys. We present an adaptation to radio data of lensfit, a method for galaxy shape measurement originally developed and used for optical weak lensing surveys. This likelihood method uses an analytical galaxy model and makes a Bayesian marginalization of the likelihood over uninteresting parameters. It has the feature of working directly in the visibility domain, which is the natural approach to adopt with radio interferometer data, avoiding systematics introduced by the imaging process. As a proof of concept, we provide results for visibility simulations of individual galaxies with flux density S ≥ 10 μJy at the phase centre of the proposed SKA1-MID baseline configuration, adopting 12 frequency channels in the band 950–1190 MHz. Weak lensing shear measurements from a population of galaxies with realistic flux and scalelength distributions are obtained after natural gridding of the raw visibilities. Shear measurements are expected to be affected by ‘noise bias’: we estimate the bias in the method as a function of signal-to-noise ratio (SNR). We obtain additive and multiplicative bias values that are comparable to SKA1 requirements for SNR > 18 and SNR > 30, respectively. The multiplicative bias for SNR >10 is comparable to that found in ground-based optical surveys such as CFHTLenS, and we anticipate that similar shear measurement calibration strategies to those used for optical surveys may be used to good effect in the analysis of SKA radio interferometer data

Stereoselective synthesis towards unnatural proline-based amino acids

A catalytic diastereoselective Mannich reaction promoted by chiral bifunctional urea-type organocatalysts has been developed. Treatment of N-Boc-3-ketoproline with N-Boc-aldimines under mild conditions afforded the corresponding unnatural proline based amino acid derivatives with excellent diastereoselectivities (up to 99:1) and enantioselectivities (up to 97% ee). The relative configuration of the chiral reaction products was deduced by the comparsion of the experimentally observed ECD spectra to that obtained theorectically

Primary beam effects of radio astronomy antennas -- II. Modelling the MeerKAT L-band beam

After a decade of design and construction, South Africa's SKA-MID precursor MeerKAT has begun its science operations. To make full use of the widefield capability of the array, it is imperative that we have an accurate model of the primary beam of its antennas. We have taken available L-band full-polarization 'astro-holographic' observations of three antennas and a generic electromagnetic simulation and created sparse representations of the beams using principal components and Zernike polynomials. The spectral behaviour of the spatial coefficients has been modelled using discrete cosine transform. We have provided the Zernike-based model over a diameter of 10 deg averaged over the beams of three antennas in an associated software tool (EIDOS) that can be useful in direction-dependent calibration and imaging. The model is more accurate for the diagonal elements of the beam Jones matrix and at lower frequencies. As we get more accurate beam measurements and simulations in the future, especially for the cross-polarization patterns, our pipeline can be used to create more accurate sparse representations of MeerKAT beams.Comment: 16 pages, 18 figures. This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review. The version of record [K. M. B. Asad et al., 2021] is available online at: https://doi.org/10.1093/mnras/stab10

A Strong Jet Signature in the Late-Time Lightcurve of GW170817

We present new 0.6-10 GHz observations of the binary neutron star merger GW170817 covering the period up to 300 days post-merger, taken with the Karl G. Jansky Very Large Array, the Australia Telescope Compact Array, the Giant Metrewave Radio Telescope and the MeerKAT telescope. We use these data to precisely characterize the decay phase of the late-time radio light curve. We find that the temporal decay is consistent with a power-law slope of t^-2.2, and that the transition between the power-law rise and decay is relatively sharp. Such a slope cannot be produced by a quasi-isotropic (cocoon-dominated) outflow, but is instead the classic signature of a relativistic jet. This provides strong observational evidence that GW170817 produced a successful jet, and directly demonstrates the link between binary neutron star mergers and short-hard GRBs. Using simple analytical arguments, we derive constraints on the geometry and the jet opening angle of GW170817. These results are consistent with those from our companion Very Long Baseline Interferometry (VLBI) paper, reporting superluminal motion in GW170817.Comment: 11 pages, 3 figures, 3 tables. Accepted for publication in ApJ Letter

Faceting for direction-dependent spectral deconvolution

Reproduced with permission from Astronomy & Astrophysics, © 2018 ESO. Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.The new generation of radio interferometers is characterized by high sensitivity, wide fields of view and large fractional bandwidth. To synthesize the deepest images enabled by the high dynamic range of these instruments requires us to take into account the direction-dependent Jones matrices, while estimating the spectral properties of the sky in the imaging and deconvolution algorithms. In this paper we discuss and implement a wideband wide-field spectral deconvolution framework (ddfacet) based on image plane faceting, that takes into account generic direction-dependent effects. Specifically, we present a wide-field co-planar faceting scheme, and discuss the various effects that need to be taken into account to solve for the deconvolution problem (image plane normalization, position-dependent Point Spread Function, etc). We discuss two wideband spectral deconvolution algorithms based on hybrid matching pursuit and sub-space optimisation respectively. A few interesting technical features incorporated in our imager are discussed, including baseline dependent averaging, which has the effect of improving computing efficiency. The version of ddfacet presented here can account for any externally defined Jones matrices and/or beam patterns.Peer reviewe

Course of psychotic experiences and disorders among apprentice traditional health practitioners in rural South Africa:3-year follow-up study

Background: Culture is inevitably linked with the experience, interpretation and course of what modern biomedicine understands to be psychotic symptoms. However, data on psychoses in low- and middle-income countries are sparse. Our previous study showed that psychotic and mood-related experiences, symptoms and disorders are common among individuals who had received the ancestral calling to become a traditional health practitioner (THP) in rural KwaZulu-Natal, South Africa. Our related ethnographic study suggested that ukuthwasa (the training to become a THP) may positively moderate these calling-related symptoms. As far as we know, no research has been conducted into the course of psychiatric symptoms among apprentice THPs. Objective: We studied the course of psychotic experiences, symptoms and disorders among apprentice THPs. We also assessed their level of functioning and expanded our knowledge on ukuthwasa. Materials and methods: We performed a 3-year follow-up of a baseline sample of apprentice THPs (n = 48). Psychiatric assessments (CAPE, SCAN), assessment of functioning (WHODAS) and a semi-structured qualitative questionnaire were completed for 42 individuals. Results: At 3-year follow-up, psychotic experiences were associated with significantly less distress and there was a reduction in frequency of psychotic symptoms compared to baseline. The number of participants with psychotic disorders had decreased from 7 (17%) to 4 (10%). Six out of seven participants (86%) with a psychotic disorder at baseline no longer had a psychiatric diagnosis at follow-up. Although the mean level of disability among the (apprentice) THPs corresponded with the 78th percentile found in the general population, 37 participants (88%) reported no or mild disability. Forty-one participants (98%) reported that ukuthwasa had positively influenced their psychiatric symptoms. Conclusion: In rural KwaZulu-Natal, psychotic experiences, symptoms and disorders have a benign course in most individuals who are undergoing the process of becoming a THP. Ukuthwasa may be an effective, culturally sanctioned, healing intervention for some selected individuals, potentially because it reframes distressing experiences into positive and highly valued experiences, reduces stigma, and enhances social empowerment and identity construction. This implies that cultural and spiritual interventions can have a positive influence on the course of psychosis

MeerKAT's discovery of a radio relic in the bimodal merging cluster A2384

We present the discovery of a single radio relic located at the edge of the galaxy cluster A2384, using the MeerKAT radio telescope. A2384 is a nearby ($z$ = 0.092), low mass, complex bimodal, merging galaxy cluster that displays a dense X-ray filament ($\sim$ 700 kpc in length) between A2384(N) (Northern cluster) and A2384(S) (Southern cluster). The origin of the radio relic is puzzling. By using the MeerKAT observation of A2384, we estimate that the physical size of the radio relic is 824 $\times$ 264 kpc$^{2}$ and that it is a steep spectrum source. The radio power of the relic is $P_{1.4\mathrm{GHz}}$ $\sim$ (3.87 $\pm$ 0.40) $\times$ 10$^{23}$ W Hz$^{-1}$. This radio relic could be the result of shock wave propagation during the passage of the low-mass A2384(S) cluster through the massive A2384(N) cluster, creating a trail appearing as a hot X-ray filament. In the previous GMRT 325 MHz observation we detected a peculiar FR I radio galaxy interacting with the hot X-ray filament of A2384, but the extended radio relic was not detected; it was confused with the southern lobe of the FR I galaxy. This newly detected radio relic is elongated and perpendicular to the merger axis, as seen in other relic clusters. In addition to the relic, we notice a candidate radio ridge in the hot X-ray filament. The physical size of the radio ridge source is $\sim$ 182 $\times$ 129 kpc$^{2}$. Detection of the diffuse radio sources in the X-ray filament is a rare phenomenon, and could be a new class of radio source found between the two merging clusters of A2384(N) and A2384(S).Comment: 12 pages, 6 figures, accepted in MNRA