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While observations of the stationary component of pulsar radio signals have in many ways formed the basis of our understanding of radio pulsars, the statistical deviations of these signals contain information that has become increasingly relevant. Using high time–frequency resolution data from the MeerKAT telescope, we study the self-noise of the autocorrelation function of six radio pulsars. The self-noise of the autocorrelation function is used to investigate the statistics of the observed radio signals on nanosecond time-scales and for five pulsars it is found to deviate from the expected form for a Gaussian process. Comparing the measured distribution of the intensity fluctuations of the on-pulse window to simulated models, we find that a mixture model comprising a Gaussian process and a Bernoulli-sampled Gaussian process is able to produce the excess self-noise while also producing the observed distribution of intensities. The parameters of the mixture model describing the signals are estimated for three of the pulsars in our sample group. Studies of the statistics presented in this work provide observational information for constraining the numerous theories of pulsar radio emission mechanisms. The mixture model suggested in this work would produce excess timing residuals for high signal-to-noise ratio observations when compared to that expected for a Gaussian process. Additionally, the measure of spectral self-noise provides a means of separating Gaussian and non-Gaussian processes that provides a potential basis for the development of alternative pulsar detection algorithms.

The inner $\sim$200 pc region of the Galaxy contains a 4 million M$_{\odot}$ supermassive black hole (SMBH), significant quantities of molecular gas, and star formation and cosmic ray energy densities that are roughly two orders of magnitude higher than the corresponding levels in the Galactic disk. At a distance of only 8.2 kpc, the region presents astronomers with a unique opportunity to study a diverse range of energetic astrophysical phenomena, from stellar objects in extreme environments, to the SMBH and star-formation driven feedback processes that are known to influence the evolution of galaxies as a whole. We present a new survey of the Galactic center conducted with the South African MeerKAT radio telescope. Radio imaging offers a view that is unaffected by the large quantities of dust that obscure the region at other wavelengths, and a scene of striking complexity is revealed. We produce total intensity and spectral index mosaics of the region from 20 pointings (144 hours on-target in total), covering 6.5 square degrees with an angular resolution of 4$"$,at a central frequency of 1.28 GHz. Many new features are revealed for the first time due to a combination of MeerKAT's high sensitivity, exceptional $u,v$-plane coverage, and geographical vantage point. We highlight some initial survey results, including new supernova remnant candidates, many new non-thermal filament complexes, and enhanced views of the Radio Arc Bubble, Sgr A and Sgr B regions. This project is a SARAO public legacy survey, and the image products are made available with this article., Comment: 29 pages, 15 figures, 3 tables, accepted for publication in the The Astrophysical Journal. Replacement arXiv version with higher quality figures

MeerKAT's large number of antennas, spanning 8 km with a densely packed 1 km core, create a powerful instrument for wide-area surveys, with high sensitivity over a wide range of angular scales. The MeerKAT Galaxy Cluster Legacy Survey (MGCLS) is a programme of long-track MeerKAT L-band (900-1670 MHz) observations of 115 galaxy clusters, observed for $\sim$6-10 hours each in full polarisation. The first legacy product data release (DR1), made available with this paper, includes the MeerKAT visibilities, basic image cubes at $\sim$8" resolution, and enhanced spectral and polarisation image cubes at $\sim$8" and 15" resolutions. Typical sensitivities for the full-resolution MGCLS image products are $\sim$3-5 {\mu}Jy/beam. The basic cubes are full-field and span 4 deg^2. The enhanced products consist of the inner 1.44 deg^2 field of view, corrected for the primary beam. The survey is fully sensitive to structures up to $\sim$10' scales and the wide bandwidth allows spectral and Faraday rotation mapping. HI mapping at 209 kHz resolution can be done at $0, Comment: 43 pages, 33 figures, 6 tables. Accepted for publication in Astronomy and Astrophysics

The Galactic Centre contains a supermassive black hole with a mass of 4 million suns within an environment that differs markedly from that of the Galactic disk. While the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings. Also, while the levels of star formation in the Galactic Centre have been approximately constant over the last few hundred Myr, there is evidence of elevated short-duration bursts, strongly influenced by interaction of the black hole with the enhanced gas density present within the ring-like Central Molecular Zone at Galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. The inner 200 pc region is characterized by large amounts of warm molecular gas, a high cosmic ray ionization rate, unusual gas chemistry, enhanced synchrotron emission, and a multitude of radio-emitting magnetised filaments, the origin of which has not been established. Here we report radio imaging that reveals bipolar bubbles spanning 1 degree x 3 degrees (140 parsecs x 430 parsecs), extending above and below the Galactic plane and apparently associated with the Galactic Centre. The structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the Galactic Centre. We estimate the age of the bubbles to be a few million years, with a total energy of 7 x 10^52 ergs. We postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the Galactic Centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities., 25 pages, 3 figures, 3 tables, authors' version of a Letter published in Nature on 11 September 2019

We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one $\approx 68'$ FWHM primary beam area with $7.6''$ FWHM resolution and $0.55 \pm 0.01$ $\mu$Jy/beam rms noise. Its J2000 center position $\alpha=04^h 13^m 26.4^s$, $\delta=-80^\circ 00' 00''$ was selected to minimize artifacts caused by bright sources. We introduce the new 64-element MeerKAT array and describe commissioning observations to measure the primary beam attenuation pattern, estimate telescope pointing errors, and pinpoint $(u,v)$ coordinate errors caused by offsets in frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the DEEP2 confusion $P(D)$ distribution from $0.25$ to $10$ $\mu$Jy with counts of individual DEEP2 sources between $10$ $\mu$Jy and $2.5$ mJy. Most sources fainter than $S \sim 100$ $\mu$Jy are distant star-forming galaxies obeying the FIR/radio correlation, and sources stronger than $0.25$ $\mu$Jy account for $\sim93\%$ of the radio background produced by star-forming galaxies. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent with the Madau & Dickinson (2014) model for the evolution of star-forming galaxies based on UV and infrared data underpredicts our 1.4 GHz source count in the range $-5 \lesssim \log[S(\mathrm{Jy})] \lesssim -4$., Comment: 20 pages, 18 figures. Accepted for publication in ApJ

New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100x larger than during its dormant state. The X-ray flux one month after reactivation was at least 800x larger than during quiescence, and has been decaying exponentially on a 111+/-19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation., Comment: Published in ApJ (2018 April 5); 13 pages, 4 figures

A new 1.4 GHz 19-element, dual-polarization, cryogenic phased array feed (PAF) radio astronomy receiver has been developed for the Robert C. Byrd Green Bank Telescope (GBT) as part of FLAG (Focal L-band Array for the GBT) project. Commissioning observations of calibrator radio sources show that this receiver has the lowest reported beamformed system temperature ($T_{\rm sys}$) normalized by aperture efficiency ($\eta$) of any phased array receiver to date. The measured $T_{\rm sys}/\eta$ is $25.4 \pm 2.5$ K near 1350 MHz for the boresight beam, which is comparable to the performance of the current 1.4 GHz cryogenic single feed receiver on the GBT. The degradation in $T_{\rm sys}/\eta$ at $\sim$ 4 arcmin (required for Nyquist sampling) and $\sim$ 8 arcmin offsets from the boresight is, respectively, $\sim$ 1\% and $\sim$ 20\% of the boresight value. The survey speed of the PAF with seven formed beams is larger by a factor between 2.1 and 7 compared to a single beam system depending on the observing application. The measured performance, both in frequency and offset from boresight, qualitatively agree with predictions from a rigorous electromagnetic model of the PAF. The astronomical utility of the receiver is demonstrated by observations of the pulsar B0329+54 and an extended HII region, the Rosette Nebula. The enhanced survey speed with the new PAF receiver will enable the GBT to carry out exciting new science, such as more efficient observations of diffuse, extended neutral hydrogen emission from galactic in-flows and searches for Fast Radio Bursts., Comment: 24 pages, 16 figures, to appear in Astronomical Journal

In 1969 a group of hunter-gatherer San were studied (Am J Clin Nutr 1971;24:229-42). Their state of hematological nutrition was excellent with a negligible incidence of iron, folate, or vitamin B12 deficiency. A genetically and linguistically similar San community who have been settled for the past 15 yr were the subjects of the present study. Anemia, due in the main to iron and/or folate deficiency, has become more common. Alcoholism has become rife in both sexes and all age groups. Our findings show that a settled lifestyle has resulted in a significant deterioration in the San's hematological nutrition.

Sera from 242 South African blacks with hepatocellular carcinoma were assayed for unsaturated vitamin B12 binding capacity (UBBC) and vitamin B12 activity. Six patients were younger than 20 years of age, and 24% were younger than 30 years of age. Eighty-four percent of the patients had a slightly raised UBBC and 86% had a slightly elevated vitamin B12 value, but in no patient was an exceptionally high UBBC present. Serum UBBC and vitamin B12 were not higher in younger patients, and raised UBBC values were not related to serum alpha-fetoprotein values. Serum UBBC and vitamin B12 concentrations were not significantly different in patients with and without coexisting cirrhosis. In none of the patients with a UBBC above 3000 pg/ml was the fibrolamellar variant of hepatocellular carcinoma present. The authors conclude that South African blacks with hepatocellular carcinoma do not secrete an abnormal vitamin B12 binding protein.

Biliary excretion of cobalamin was studied in baboons after intravenous injection of 57 Co-radio-labeled cyanocobalamin. Radioactivity appeared in bile after 20 min, and up to 4.4% of the dose was recovered in 6 h. It was estimated that 4 μg cobalamin traverses the baboon biliary tract each day. These studies in the nonhuman primate confirm that there is considerable biliary excretion of cobalamin and that enterohepatic circulation of the vitamin is important for maintenance of normal cobalamin balance.

A method is described for the measurement of vitamin B-12 (B-12) in solid tissues by radioisotope dilution (RID) assay. The method is a modification using double extraction of a serum B-12 RID assay which uses chicken serum as the B-12 binder. The method was developed and tested using human and bat liver specimens. Double extraction was shown to be more efficient than single extraction, and resulted in complete release of endogenous liver [ 57 Co]B-12 administered to bats. Results using the RID assay in 16 human and 17 bat liver specimens were compared with those obtained using the Lactobacillus leichmannii microbiological assay. Correlation was good, but the RID assay gave higher results. Lower results using the microbiological assay appear to be due to inadequate extraction of B-12 from tissues.

1. The effect of methylcobalamin inactivation by the anaesthetic gas nitrous oxide on the activity of the cobalamin-dependent methionine synthetase (5-methyltetrahydrofolate homocysteine methyltransferase; EC 2.1. I. 13) reaction, and on DNA synthesis, in the fruit bat Rousettus aegyptiucus, was examined.2. Methionine synthetase activity in the liver of bats exposed to N2O—oxygen (50: 50, v/v) for 90 min/d averaged 32% of that of controls after 4 d of exposure and only 5% after 12–14 weeks of exposure.3. DNA synthesis in the bone marrow, as reflected by the deoxyuridine suppression test, was unaffected by 4 d of exposure to N2O and only minimally affected after 5–10 weeks of exposure.4. These results suggest that DNA synthesis in the fruit bat is unusually resistant to inhibition of methionine synthetase and imply the existence of a non-methylated circulating folate pool in this species.

The prevalence of anaemia and deficiencies of iron, folate and vitamin B12 were investigated in 140 rural black preschool children aged 3-5 years living in five different villages in the Letaba area, near Tzaneen. Anaemia was highly prevalent, 39.2% of the children having haemoglobin levels below 11.1 g/dl. Approximately 10% were considered to be iron-deficient. On the basis of subnormal red cell folate values, 1 in 4 children was folate-deficient, suggesting the need for intervention at the community level such as enrichment of the staple foodstuff, maize meal, with folic acid.

Ferritin levels in serum and milk were investigated in series of 15 urban and 18 rural black mothers. No mother was anaemic. Mean serum ferritin levels in the urban and rural groups were 57 +/- 55 ug/l and 25 +/- 28 ug/l (mean +/- SD). Corresponding milk ferritin concentrations were 21 +/- 22 ug/l and 29 +/- 30 ug/l respectively. The significance of ferritin in human milk is discussed.

The C2 probe detects a single fragment (Table 1) in each DNA sample. This fragment shows the same allelic micro-heterogeneity (Table 2 and Fig. 1) as previously described (1) for SstI digests. However, because of the small size differences among the HindIII fragments, it is not possible to assign each fragment to its appropriate allele. Consequently, only two alleles have been defined for this enzyme/probe combination. The 4.46 kb band includes the three longest fragments described by Bentley et al. (1), and the 4.32 kb band is equivalent to the shortest allelic fragment of Bentley.

Twenty-eight fragments have been defined using the class I probe (Table 1 and Fig. 1). The family studies have revealed the existence of a few additional faint bands that are not detected in every blot. The majority of the fragments are polymorphic, although many of their frequencies are either above 85% or below 15%. Most individual DNA samples display 15 to 18 bands which correlate well both in number and size with those reported (1,2). There is no relationship between RFLP pattern and DR type (Table 2).

The DQ alpha probe detects five bands. Bands 1-4 are allelic and correlate broadly, but not exclusively, with the DR types of the cells (Table 2). Band 5 is the DQA2 gene (1,2).

The 210H probe detects bands of three size classes (Fig. 1, Table 1). Std. band 1 contains one fragment of 30.50 kb encompassing the nonpolymorphic 210HB gene (1) and also, in “long” C4B haplotypes (2), a second fragment containing the 210HA gene. In “short” C4B haplotypes the 210HA gene is detected on a 25.19 kb band (std. band 2). The difference between the two haplotypes is determined by the presence or absence of an intron of ∼6.5 kb in the C4B gene. Std. band 3 (19.57 kb) is found in only two DNA samples, lanes 4 and 27 (WS 9107 and 9028, Table 2) and is due to DNA rear-rangements in the C4/210H loci (see also C4/HindIII report).

Absorption of radiolabeled cobalamin in baboons was assessed by whole body counting. Retention of biliary cobalamin and an aqueous solution of cyanocobalamin was measured in normal baboons and in baboons after total gastrectomy by using 57Co-labeled biliary cobalamin and 58C0-cyanocobalamin, with and without baboon gastric juice containing intrinsic factor. Radiolabeled biliary cobalamin was obtained by intravenous injection of 57Co-cyanocobalamin in baboons and collection of bile through a cannula placed in the common bile duct. Cobalamin absorption was not completely abolished by gastrectomy and biliary cobalamin was better retained than cyanocobalamin; intrinsic factor enhanced absorption of both forms. After gastrectomy there was steady depletion of liver and serum cobalamin levels, which ceased after a new equilibrium was reached between a progressively diminishing cobalamin loss and the impaired but significant residual level of absorption. These studies in the nonhuman primate provide further information concerning the enterohepatic circulation of cobalamin and suggest that the form of cobalamin in bile may be more readily absorbed than is cyanocobalamin or that bile itself may have an enhancing effect on cobalamin absorption. The data also suggest that physiologically significant amounts of cobalamin may be absorbed in the absence of a gastric source of intrinsic factor.

Seven standard bands have been defined using the C4 probe (Table 1). Band 3 (19.26 kb) is only found in one sample (WT8,9017) and is probably a partial digestion product of bands 5 and 7 (Table 2 and Fig. 1). Band 4 is found in all nondeletion haplotypes and constitutes the 3’ half of the C4A gene. In many C4A deletion haplotypes (1), (lanes 13,15, and 31: WS.ID. 9022,9023, and 9088, respectively) st. band 4 is replaced by an 8.0 kb band (st. band 6), which is produced as a result of the fusion of the C4A and C4B genes.

Serum human pancreatic polypeptide (hPP) responses to 50 gm. of oral glucose and a 25 gm. intravenous bolus of glucose were measured in 10 healthy human volunteers. Oral glucose caused a 50% rise, whereas I.V. glucose caused a 35% fall in hPP concentration. There was no relationship between the absolute glucose concentration or the change in glucose level and the PP concentration. It is suggested that oral and I.V. glucose affect PP by indirect mechanisms and that PP may be involved in carbohydrate metabolism in man.

In healthy young adults, serum levels of cobalamin, unsaturated and total cobalamin binding capacity, and transcobalamin (TC) II are significantly higher in females, while TC III is higher in males. These findings have relevance to the reference values in normals for these tests.

Thirty-four bands were identified in the DQB/HID system (Table 1 and Fig. 1). The distribution of nineteen bands showing high DQB specificity is shown in Table 2.

Two nonpolymorphic, low molecular weight bands (Table 1) are produced by this enzyme/probe combination (Fig. 1). The 5’ end of the Bf gene is probably contained in the less intense, 2.86 kb band (standard band 2) and the majority of the coding sequence, up to the 3’end, lies in the 4.52 kb band (1).

Biliary excretion of cobalamin was studied in baboons after intravenous injection of 57Co-radiolabeled cyanocobalamin. Radioactivity appeared in bile after 20 min, and up to 4.4% of the dose was recovered in 6 h. It was estimated that 4 microgram cobalamin traverses the baboon biliary tract each day. These studies in the nonhuman primate confirm that there is considerable biliary excretion of cobalamin and that enterohepatic circulation of the vitamin is important for maintenance of normal cobalamin balance.

HAEMATOLOGICAL and neurological sequelae are the two major effects of vitamin B12 deficiency in man. In the haemopoietic system, megaloblastic change leading to anaemia seems to be caused by deranged DNA synthesis1. The cause of central nervous system demyelination, however, is unknown and progress in this area has been hampered by the lack of a suitable experimental animal model. We report that Egyptian fruit bats (Rousettus aegyptiacus), made vitamin B12 deficient in captivity, develop neurological changes similar to those observed in human subacute combined degeneration of the spinal cord.

1. The effect of methylcobalamin inactivation by the gas nitrous oxide on plasma amino acid and tissue methionine levels in fruit bats (Rousettus aegyptiacus) was examined.2. Animals exposed to N2O-oxygen (1:1, v/v) for 90 min daily received a fruit diet with or without methionine or betaine supplements. Exposure and diets were continued for up to 17 weeks or until neurological impairment and muscular weakness was established.3. All the groups exposed to N2O had significantly lower liver, brain and plasma methionine concentrations except the methionine-supplemented animals which showed significantly raised levels. Plasma homocysteine, which was absent in controls, was present in all the N2O-exposed groups.4. Betaine supplementation resulted in reduced accumulation of homocysteine in plasma. However, plasma and liver methionine levels were only slightly increased compared with animals on the basal diet, and brain methionine levels were the lowest of all the groups studied.5. These results support the hypothesis that reduced methionine synthesis is an important contributor to the development of neurological impairment in this species and suggest that dietary supplementation with the methionine precursor betaine cannot replace the loss of vitamin B12-dependent methionine synthesis.

We present the results of commissioning observations for a new digital beamforming back end for the Focal plane L-band Array for the Robert C. Byrd Green Bank Telescope (FLAG), a cryogenically cooled Phased Array Feed (PAF) with the lowest measured T_sys/eta of any PAF outfitted on a radio telescope to date. We describe the custom software used to apply beamforming weights to the raw element covariances to create research quality spectral line images for the new fine-channel mode, study the stability of the beam weights over time, characterize FLAG's sensitivity over a frequency range of 150 MHz, and compare the measured noise properties and observed distribution of neutral hydrogen emission from several extragalactic and Galactic sources with data obtained with the current single-pixel L-band receiver. These commissioning runs establish FLAG as the preeminent PAF receiver currently available for spectral line observations on the world's major radio telescopes., 28 ages, 18 figures. Accepted for publication in the Astronomical Journal