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To mitigate the effects of Radio Frequency Interference (RFI) on the data analysis pipelines of 21 cm interferometric instruments, numerous inpaint techniques have been developed. In this paper, we examine the qualitative and quantitative errors introduced into the visibilities and power spectrum due to inpainting. We perform our analysis on simulated data as well as real data from the Hydrogen Epoch of Reionization Array (HERA) Phase 1 upper limits. We also introduce a convolutional neural network that is capable of inpainting RFI corrupted data. We train our network on simulated data and show that our network is capable of inpainting real data without requiring to be retrained. We find that techniques that incorporate high wavenumbers in delay space in their modelling are best suited for inpainting over narrowband RFI. We show that with our fiducial parameters discrete prolate spheroidal sequences (dpss) and clean provide the best performance for intermittent RFI while Gaussian progress regression (gpr) and least squares spectral analysis (lssa) provide the best performance for larger RFI gaps. However, we caution that these qualitative conclusions are sensitive to the chosen hyperparameters of each inpainting technique. We show that all inpainting techniques reliably reproduce foreground dominated modes in the power spectrum. Since the inpainting techniques should not be capable of reproducing noise realizations, we find that the largest errors occur in the noise dominated delay modes. We show that as the noise level of the data comes down, clean and dpss are most capable of reproducing the fine frequency structure in the visibilities.

We present a Bayesian jackknife test for assessing the probability that a data set contains biased subsets, and, if so, which of the subsets are likely to be biased. The test can be used to assess the presence and likely source of statistical tension between different measurements of the same quantities in an automated manner. Under certain broadly applicable assumptions, the test is analytically tractable. We also provide an open-source code, chiborg, that performs both analytic and numerical computations of the test on general Gaussian-distributed data. After exploring the information theoretical aspects of the test and its performance with an array of simulations, we apply it to data from the Hydrogen Epoch of Reionization Array (HERA) to assess whether different sub-seasons of observing can justifiably be combined to produce a deeper 21 cm power spectrum upper limit. We find that, with a handful of exceptions, the HERA data in question are statistically consistent and this decision is justified. We conclude by pointing out the wide applicability of this test, including to CMB experiments and the H0 tension.

We present a framework for identifying and flagging malfunctioning antennas in large radio interferometers. We outline two distinct categories of metrics designed to detect outliers along known failure modes of large arrays: cross‐correlation metrics, based on all antenna pairs, and auto‐correlation metrics, based solely on individual antennas. We define and motivate the statistical framework for all metrics used, and present tailored visualizations that aid us in clearly identifying new and existing systematics. We implement these techniques using data from 105 antennas in the Hydrogen Epoch of Reionization Array (HERA) as a case study. Finally, we provide a detailed algorithm for implementing these metrics as flagging tools on real data sets.

Precision calibration poses challenges to experiments probing the redshifted 21-cm signal of neutral hydrogen from the Cosmic Dawn and Epoch of Reionization (z ∼ 30–6). In both interferometric and global signal experiments, systematic calibration is the leading source of error. Though many aspects of calibration have been studied, the overlap between the two types of instruments has received less attention. We investigate the sky based calibration of total power measurements with a HERA dish and an EDGES-style antenna to understand the role of autocorrelations in the calibration of an interferometer and the role of sky in calibrating a total power instrument. Using simulations we study various scenarios such as time variable gain, incomplete sky calibration model, and primary beam model. We find that temporal gain drifts, sky model incompleteness, and beam inaccuracies cause biases in the receiver gain amplitude and the receiver temperature estimates. In some cases, these biases mix spectral structure between beam and sky resulting in spectrally variable gain errors. Applying the calibration method to the HERA and EDGES data, we find good agreement with calibration via the more standard methods. Although instrumental gains are consistent with beam and sky errors similar in scale to those simulated, the receiver temperatures show significant deviations from expected values. While we show that it is possible to partially mitigate biases due to model inaccuracies by incorporating a time-dependent gain model in calibration, the resulting errors on calibration products are larger and more correlated. Completely addressing these biases will require more accurate sky and primary beam models.

We analyze data from the Hydrogen Epoch of Reionization Array (HERA). This is the third in a series of papers on the closure phase delay spectrum technique designed to detect the H i 21 cm emission from cosmic reionization. We present the details of the data and models employed in the power spectral analysis and discuss limitations to the process. We compare images and visibility spectra made with HERA data to parallel quantities generated from sky models based on the Galactic and Extra-Galactic All-Sky MWA (GLEAM) survey, incorporating the HERA telescope model. We find reasonable agreement between images made from HERA data with those generated from the models, down to the confusion level. For the visibility spectra, there is broad agreement between model and data across the full band of ∼80 MHz. However, models with only GLEAM sources do not reproduce a roughly sinusoidal spectral structure at the tens of percent level seen in the observed visibility spectra on scales of ∼10 MHz on 29 m baselines. We find that this structure is likely due to diffuse Galactic emission, predominantly the Galactic plane, filling the far sidelobes of the antenna primary beam. We show that our current knowledge of the frequency dependence of the diffuse sky radio emission, and the primary beam at large zenith angles, is inadequate to provide an accurate reproduction of the diffuse structure in the models. We discuss some implications arising due to this missing structure in the models, in terms of calibration, and in the search for the H i 21 cm signal, as well as possible mitigation techniques.

We present a study of internal reflection and cross-coupling systematics in Phase I of the Hydrogen Epoch of Reionization Array (HERA). In a companion paper, we outlined the mathematical formalism for such systematics and presented algorithms for modeling and removing them from the data. In this work, we apply these techniques to data from HERA's first observing season as a method demonstration. The data show evidence for systematics that, without removal, would hinder a detection of the 21 cm power spectrum for the targeted Epoch of Reionization (EoR) line-of-sight modes in the range 0.2 h Mpc < $" SRC="apjab5e8aieqn1.gif"/ < 0.5 h Mpc . In particular, we find evidence for nonnegligible amounts of spectral structure in the raw autocorrelations that overlaps with the EoR window and is suggestive of complex instrumental effects. Through systematic modeling on a single night of data, we find we can recover these modes in the power spectrum down to the integrated noise floor, achieving a dynamic range in the EoR window of 10 in power (mK units) with respect to the bright galactic foreground signal. Future work with deeper integrations will help determine whether these systematics can continue to be mitigated down to EoR levels. For future observing seasons, HERA will have upgraded analog and digital hardware to better control these systematics in the field. -1 -1 -1 -1 6 2

We discuss absolute calibration strategies for Phase I of the Hydrogen Epoch of Reionization Array (HERA), which aims to measure the cosmological 21 cm signal from the Epoch of Reionization. HERA is a drift-scan array with a 10° wide field of view, meaning bright, well-characterized point-source transits are scarce. This, combined with HERA's redundant sampling of the uv plane and the modest angular resolution of the Phase I instrument, make traditional sky-based and self-calibration techniques difficult to implement with high dynamic range. Nonetheless, in this work, we demonstrate calibration for HERA using point-source catalogs and electromagnetic simulations of its primary beam. We show that unmodeled diffuse flux and instrumental contaminants can corrupt the gain solutions and present a gain-smoothing approach for mitigating their impact on the 21 cm power spectrum. We also demonstrate a hybrid sky and redundant calibration scheme and compare it to pure sky-based calibration, showing only a marginal improvement to the gain solutions at intermediate delay scales. Our work suggests that the HERA Phase I system can be well calibrated for a foreground avoidance power spectrum estimator by applying direction-independent gains with a small set of degrees of freedom across the frequency and time axes.

English: Regardless of past research, great uncertainty still exists amongst the research community, fertilizer agents and farmers alike with regard to the benefits of foliar inorganic fertilizer application for crop production. This supplied a rationale for investigating foliar nutrition as an agricultural practice, with the main aim of increasing maize kernel yield, under standard farm management practices. Fertilizer salts used in this study included potassium nitrate (KNO3), mono potassium phosphate (MKP) and mono ammonium phosphate (MAP). Three objectives were set in order to obtain information about i) the optimal application growth stage (2004/05 season), ii) the optimum concentration rate (2005/06 season) and iii) the contribution of either the P or K moiety (or both) contained in foliar applied salts towards growth, physiological and yield responses measured in maize (2006/07 season). During the 2004/05 season a 4% solution of MKP and a 3% solution of KNO3 were applied at growth stages V3 and V8. MKP applied at V8 was the best treatment as it increased plant height significantly (11%) as well as plant fresh and dry mass markedly, compared to the control, when measured at the end of the vegetative growth period at V19. The higher yield (+23%) obtained with MKP applied at V8 during season one, compared to treatment at V3, corresponded with an increase in grain filling of the second ear (+16%), total ear mass (+20%), kernel mass (+20%) and number of kernels (+16%) as well as higher total sugar and starch that accumulated in kernels. During the 2005/06 season, vegetative growth and yield parameters showed no significant differences between the single and double rates for both salts applied at V8. However, MKP applied at both the single and double rates contributed to marked yield increases of 12% and 14% respectively. Although neither KNO3 nor MKP significantly influenced chlorophyll content or photosynthesis efficacy (chlorophyll a fluorescence), higher sugar, Afrikaans: Ten spyte van vorige navorsing bestaan daar nog groot onsekerheid tussen navorsers, bemestingsagente en boere ten opsigte van die potensiële voordele, al dan nie, wat blaartoegediende bemestingstowwe vir gewasproduksie inhou. Dit het ‘n rasionaal verskaf vir onderhawige ondersoek na blaarbemesting as ‘n landboupraktyk met die hoofdoel om die opbrengs van mielies onder standaard plaasbestuurspraktyke te verhoog. Bemestingsoute wat in die studie gebruik is het kaliumnitraat (KNO3), mono kaliumfosfaat (MKP) en mono ammonium fosfaat (MAP) tegnies ingesluit. Drie doelwitte is geformuleer ten einde inligting te bekom betreffende i) die optimum toedieningstyd (2004/05 seisoen), ii) die optimum konsentrasie (2005/06 seisoen) en iii) die moontlike bydra van P of K of albei om ‘n groei-, fisiologiese- en/of opbrengsrespons by mielies te ontlok (2006/07 seisoen). Tydens die 2004/05 seisoen is ‘n 4% MKP en ‘n 3% KNO3 oplossing apart toegedien op groeistadia V3 en V8. MKP, op V8 toegedien, was die beste behandeling in die sin dat dit planthoogte betekenisvol (11%) sowel as plant vars- en droë massa merkbaar verhoog het teen die einde van die groeiseisoen op stadium V19, in vergelyking met die onbehandelde kontrole. Verder het die hoër opbrengs (+23%) wat met die MKP behandeling op V8 tydens die eerste seisoen bekom is ooreengestem met ‘n verhoging in graanvulling van die tweede kop (+16%), totale kopmassa (+20%), pitmassa (+20%) en aantal pitte per kop (+16%) asook hoër suiker- en stysel akkumulasie in graan in vergelyking met behandeling op die V3 groeistadium. In die 2005/06 seisoen is geen verskille ten opsigte van vegetatiewe groei en opbrengs tussen die enkel en dubbel konsentrasie bespuitings van beide soute wat op V8 toegedien is waargeneem nie. Maar, MKP teen beide konsentrasies toegedien het bygedra tot merkbare opbrengsverhogings van 12% en 14% respektiewelik. Alhoewel nie KNO3 of MKP die chlorofilinhoud of fotosintese kapasiteit (chlorofil a fluoressensie)

English: The occurrence of cyanobacterial blooms that may be toxic is one of the major consequences of eutrophication. The prevalence of cyanobacteria and their toxins in reservoirs create a significant water quality problem and complicates the water purification process for producing safe drinking water. Microcystin is the dominant group of cyanotoxins and the most commonly occurring variant is microcystin-LR. The purpose of this study was to determine the presence of cyanotoxins in the reservoirs and drinking water supplied to the city and towns of Bloemfontein, Thaba Nchu and Botshabelo, in the central region of South Africa. To achieve this, the microcystin-LR concentrations were determined in Rustfontein, Mockes and Maselspoort Dams and the efficiency of treatment processes at Rustfontein and Maselspoort treatment plants in removing this cyanotoxin were investigated. In situ measurements of electrical conductivity (EC), dissolved oxygen (DO), pH and surface water temperature were done at two-weekly intervals over the study period. Water samples were collected and analysed upon return to the laboratory for NO3-N, PO4-P, chlorophyll-a, dominant algal species and microcystin-LR. Final treated water from Rustfontein and Maselspoort water treatment facilities was also analysed for microcystin-LR. Physico-chemical variables displayed no clear-cut seasonal trends except for surface water temperature which followed a distinctive seasonal pattern with lower values in winter and higher values in summer. The concentration of DO seemed to be influenced by water temperature, photosynthetic activity of phytoplankton, wind induced mixing and decomposition of organic matter. Based on the nutrient content, these impoundments were found to be eutrophic. However, in terms of chlorophyll-a concentrations, Maselspoort Dam was mesotrophic, Rustfontein Dam eutrophic and Mockes Dam hypertrophic. Cyanobacteria genera that were commonly found in the three impoundments were Microcystis, Afrikaans: Die voorkoms van sianobakteriële opbloeie wat moontlik toksies kan wees, is een van die gevolge van eutrofikasie. Sianobakterieë en hulle toksiene is „n probleem in opgaardamme en bemoeilik die suiwering van water, asook die voorsiening van drinkwater. Mikrosistien is die groep sianotoksiene wat die meeste voorkom en mikrosistien-LR domineer hierdie groep toksiene. Die doel van die studie was om die voorkoms van sianotoksiene in die opgaardamme en drinkwater van die stad Bloemfontein en dorpe Thaba Nchu en Botshabelo in sentraal Suid-Afrika te ondersoek. Om dit te doen is die konsentrasies mikrosistien-LR in Rustfontein-, Mockes- en Maselspoortdamme bepaal, asook in die gesuiwerde water van die Rustfontein en Maselspoort suiweringsaanlegte. In situ metings van konduktiwiteit (EC), opgeloste suurstof (DO), pH en oppervlak temperature is tweeweekliks gedurende die studietydperk gedoen. Watermonsters is versamel en na terugkeer in die laboratorium geanaliseer vir NO3-N, PO4-P, chlorofil-a, dominante alg spesies en mikrosistien-LR. Finaal gesuiwerde water van Rustfontein en Maselspoort suiweringsaanlegte is vir mikrosistien-LR getoets. Geen duidelike seisoenale patroon was herkenbaar in die fisies-chemiese resultate nie, behalwe vir watertemperatuur wat duidelik laer in die winter en hoër in die somer was. DO was duidelik beïnvloed deur watertemperatuur, fotosintetiese aktiwiteit van die fitoplankton, windvermenging en die ontbinding van organiese materiaal. Volgens die voedingstofkonsentrasies kan die opgaardamme as eutrofies geklassifiseer word. In terme van die chlorofil-a konsentrasies is Maselspoortdam mesotrofies, Rustfonteindam eutrofies en Mockesdam hipereutrofies. Die dominante sianobakteriese genera in die opgaardamme was Microcystis, Anabaena en Oscillatoria. Oscillatoria was met tye dominant in Mockersdam gevolg deur Ceratium. Microcystis was met tye dominant in Rustfonteindam. Euglenoiede soos Euglena, Trachelomonas en Phacus, wat op die teenwoor, University of the Free State, Strategic Cluster, Water Management in Water-Scarce Areas, Government of Lesotho

English: The purpose of this study was to investigate the relationship between coping and resilience in adolescents with emotional and behavioral problems, and to describe it according to relevant literature and research. The research group consisted of 150 adolescents between the ages of 15 and 18 years, and represented both genders and Afrikaans-, English- and African language groups. The Coping Response Inventory (Moos, 2004) was selected to measure the coping responses and the Resilience Scale (Wagnild & Young, 1993) to measure the resilience of the adolescents. The study findings indicate that there is a significant positive relationship between coping responses (consisting of approach coping responses and avoidance coping responses) and resilience. By implication, resilient adolescents will be more successful in the application of coping strategies, regaining balance despite adversity and find meaning amidst confusion and tumult (Wagnild, 2009)., Afrikaans: Die doel van die artikel is om die verband te bepaal tussen coping en sielkundige weerbaarheid by adolessente met em osionele- en gedragsprobleme en dit te beskryf na aanleiding van relevante literatuur en navorsing. Die ondersoekgroep het uit 150 adolessente bestaan tussen die ouderdomme van 15 en 18 jaar, en was verteenwoordigend van beide geslagte en sluit Afrikaans-, Engels- en Afrika- taalsprekende groepe in. Die Coping Response Inventory (Moos, 2004) is gebruik om die copingresponse te bepaal en die Resilience Scale (Wagnild & Young, 1993) is toegepas om die sielkundige weerbaarheid by die adoless ent te meet. Die bevindinge dui aan dat daar ‘n beduidende positiewe verband tussen coping response (wat uit twee subskale bestaan, nl. benaderings- en vermydingscoping) en sielkundige weerbaarheid is. Dit impliseer dus dat die sielkundig weerbare adol ossent meer suksesvol sal wees in die toepassing van copingstrategieë en gevolglik uitdagings beter sal hanteer, balans sal kan herstel en sinvolle response sal lewer ten spyte van die teenspoed en verwarring waarmee hy/sy gekonfronteer word (Wagnild, 2009).

English: The Modder River is a relatively small river which drains an area of 7 960 km2 in the central region of the Free State Province, South Africa and has a mean annual run-off of 184 x 106 m3. Water demand in the Modder River catchment has exceeded supply in the past which necessitated the development of two transfer schemes: 1) From the Caledon to the Modder (Caledon-Bloemfontein pipeline), and 2) The Caledon to Modder also known as the Novo transfer scheme. This study focussed on the ecological effects of the Novo transfer scheme on both the Modder and Caledon Rivers from a limnological point of view, thus excluding the human component and land-based investigations. The transfer of water from the turbid Caledon River caused an increase in turbidity in Knellpoort Dam. However, this turbidity decreased when transfer of water was terminated, and conditions returned to those prior to the transfer of the water. This increase in turbidity brought about certain effects, like limitation of underwater light penetration, and a consequent decrease of the euphotic depth. The turbidity did, however, not extend to the inflow of the dam where the Novo pump station is located and is thus not expected to increase turbidity in the Modder River. The largest fraction of sediment particles in the Caledon River, consists of very fine sand. This has implications in terms of the bioavialability of nutrients and consequently, the maximum bioavailability of nutrients in the sediment load of the Caledon River was found to 339 mg/kg N and 106 mg/kg P. The transfer of water (and nutrient-rich sediments) from the Caledon River, via Knellpoort Dam, to the Modder River caused an increase in the concentrations of TP, PO4-P, NO3-N and SiO2-Si in Knellpoort Dam. Since the effect of the inflowing water seems to be localised to the area at the inflow channel, the water quality at the Novo pump station (on the opposite side of the impoundment) was little influenced. However, if transfer takes pla, Afrikaans: Die Modderrivier (met ‘n afvloei van 184 x 106 m3 per jaar) is `n redelike klein rivier wat `n area van 7 960 km2 in die sentrale deel van die Vrystaat, Suid-Afrika dreineer. In die verlede, het die aanvraag na water die voorsiening oorskrei, wat die volgende oordragskemas tot gevolg gehad het: 1) Van die Caledon na die Modderrivier (Caledon-Bloemfontein pyplyn), en 2) Van die Caledon na die Modderrivier (ook bekend as die Novo oordragskema).Hierdie studie het gefokus op die ekologiese impak van die Novo oordragskema op beide die Caledon- en Modderrivier vanuit `n limnologiese oogpunt, en sluit dus die menslike en landelike aspekte uit. Die oordrag van water vanuit die troebel Caledonrivier het ‘n toename in troebelheid in Knellpoort dam veroorsaak. Hierdie troebelheid het egter afgeneem sodra die oordrag van water opgehou het, en toestande het teruggekeer na dié van voor die oordrag. Die toename in troebelheid het sekere impakte tot gevolg gehad, soos die beperking van ligindringing met `n gevolglike afname in die eufotiese diepte. Die toename in troebelheid het egter nie gestrek tot by die invloei van die dam waar die Novo pompstasie geleë is nie, en daar word dus nie verwag dat die troebelheid in die Modderrivier beïnvloed sal word nie. Die grootste gedeelte van die sedimentpartikels in die Caledonrivier bestaan uit baie fyn sand. Dit kan die bio-beskikbaarheid van voedingstowwe beïnvloed en gevolglik is die maksimum bioskikbaarheid van N en P bepaal. Die resultate toon dat die maksimum bio-beskikbaarheid vanaf die sedimente 339 mg/kg N en 106 mg/kg P is .Die oordrag van water (en voedingstofryke sedimente) van die Caledonrivier, via Knellpoort Dam, het `n toename veroorsaak in die konsentrasies van TP, PO4-P, NO3-N and SiO2-Si in Knellpoort dam. Aangesien die effek van die invloei gelokaliseerd was in die area van invloei, is die waterkwaliteit by die Novo pompstasie (aan die oorkant van die dam) nie beïnvloed nie. As wateroordrag egter vir lang perio, National Research Foundation (NRF)