Simultaneous observations of giant pulses from the Crab pulsar, with the Murchison Widefield Array and Parkes radio telescope: implications for the giant pulse emission mechanism

We report on observations of giant pulses from the Crab pulsar performed simultaneously with the Parkes radio telescope and the incoherent combination of the Murchison Widefield Array (MWA) antenna tiles. The observations were performed over a duration of approximately one hour at a center frequency of 1382 MHz with 340 MHz bandwidth at Parkes, and at a center frequency of 193 MHz with 15 MHz bandwidth at the MWA. Our analysis has led to the detection of 55 giant pulses at the MWA and 2075 at Parkes above a threshold of 3.5σ and 6.5σ, respectively. We detected 51% of the MWA giant pulses at the Parkes radio telescope, with spectral indices in the range of-3.6 > α > -4.9 (Sv μ ∝ Va). We present a Monte Carlo analysis supporting the conjecture that the giant pulse emission in the Crab is intrinsically broadband, the less than 100% correlation being due to the relative sensitivities of the two instruments and the width of the spectral index distribution. Our observations are consistent with the hypothesis that the spectral index of giant pulses is drawn from normal distribution of standard deviation 0.6, but with a mean that displays an evolution with frequency from −3.00 at 1382 MHz, to −2.85 at 192 MHz

The low-frequency characteristics of PSR J0437–4715 observed with the Murchison Wide-Field Array

We report on the detection of the millisecond pulsar PSR J0437–4715 with the Murchison Wide-field Array (MWA) at a frequency of 192 MHz. Our observations show rapid modulations of pulse intensity in time and frequency that arise from diffractive scintillation effects in the Interstellar Medium (ISM), as well as prominent drifts of intensity maxima in the time-frequency plane that arise from refractive effects. Our analysis suggests that the scattering screen is located at a distance of ∼80-120 pc from the Sun, in disagreement with a recent claim that the screen is closer (∼10 pc). Comparisons with higher frequency data from Parkes reveal a dramatic evolution of the pulse profile with frequency, with the outer conal emission becoming comparable in strength to that from the core and inner conal regions. As well as demonstrating the high time resolution science capabilities currently possible with the MWA, our observations underscore the potential to conduct low-frequency investigations of timing-array millisecond pulsars, which may lead to increased sensitivity in the detection of nanoHertz gravitational waves via the accurate characterization of ISM effects

Simultaneous observations of giant pulses from the Crab pulsar, with the Murchison Widefield Array and Parkes radio telescope: implications for the giant pulse emission mechanism

We report on observations of giant pulses from the Crab pulsar performed simultaneously with the Parkes radio telescope and the incoherent combination of the Murchison Widefield Array (MWA) antenna tiles. The observations were performed over a duration of approximately one hour at a center frequency of 1382 MHz with 340 MHz bandwidth at Parkes, and at a center frequency of 193 MHz with 15 MHz bandwidth at the MWA. Our analysis has led to the detection of 55 giant pulses at the MWA and 2075 at Parkes above a threshold of 3.5σ and 6.5σ, respectively. We detected 51% of the MWA giant pulses at the Parkes radio telescope, with spectral indices in the range of-3.6 > α > -4.9 (Sv μ ∝ Va). We present a Monte Carlo analysis supporting the conjecture that the giant pulse emission in the Crab is intrinsically broadband, the less than 100% correlation being due to the relative sensitivities of the two instruments and the width of the spectral index distribution. Our observations are consistent with the hypothesis that the spectral index of giant pulses is drawn from normal distribution of standard deviation 0.6, but with a mean that displays an evolution with frequency from −3.00 at 1382 MHz, to −2.85 at 192 MHz

Simultaneous observations of giant pulses from the crab pulsar, with the Murchison Widefield Array and Parkes radio telescope: implications for the giant pulse emission mechanism

We report on observations of giant pulses from the Crab pulsar performed simultaneously with the Parkes radio telescope and the incoherent combination of the Murchison Widefield Array (MWA) antenna tiles. The observations were performed over a duration of approximately one hour at a center frequency of 1382 MHz with 340 MHz bandwidth at Parkes and at a center frequency of 193 MHz with 15 MHz bandwidth at the MWA. Our analysis has led to the detection of 55 giant pulses at the MWA and 2075 at Parkes above a threshold of 3.5σ and 6.5σ, respectively. We detected 51% of the MWA giant pulses at the Parkes radio telescope, with spectral indices in the range of -3.6 > α > -4.9 (Sv ∝ vα. We present a Monte Carlo analysis supporting the conjecture that the giant pulse emission in the Crab is intrinsically broadband, the less than 100% correlation being due to the relative sensitivities of the two instruments and the width of the spectral index distribution. Our observations are consistent with the hypothesis that the spectral index of giant pulses is drawn from normal distribution of standard deviation 0.6, but with a mean that displays an evolution with frequency from −3.00 at 1382 MHz, to −2.85 at 192 MHz

Time-domain and spectral properties of pulsars at 154 MHz

We present 154 MHz Murchison Widefield Array imaging observations and variability information for a sample of pulsars. Over the declination range −80° < δ < 10°, we detect 17 known pulsars with mean flux density greater than 0.3 Jy. We explore the variability properties of this sample on time-scales of minutes to years. For three of these pulsars, PSR J0953+0755, PSR J0437−4715, and PSR J0630−2834, we observe interstellar scintillation and variability on time-scales of greater than 2 min. One further pulsar, PSR J0034−0721, showed significant variability, the physical origins of which are difficult to determine. The dynamic spectra for PSR J0953+0755 and PSR J0437−4715 show discrete time and frequency structure consistent with diffractive interstellar scintillation and we present the scintillation bandwidth and time-scales from these observations. The remaining pulsars within our sample were statistically non-variable. We also explore the spectral properties of this sample and find spectral curvature in pulsars PSR J0835−4510, PSR J1752−2806, and PSR J0437−4715

A search for Fast Radio Bursts at low frequencies with Murchison Widefield Array high time resolution imaging

We present the results of a pilot study search for Fast Radio Bursts (FRBs) using the Murchison Widefield Array (MWA) at low frequencies (139 - 170 MHz). We utilised MWA data obtained in a routine imaging mode from observations where the primary target was a field being studied for Epoch of Reionisation detection. We formed images with 2 second time resolution and 1.28~MHz frequency resolution for 10.5 hours of observations, over 400 square degrees of the sky. We de-dispersed the dynamic spectrum in each of 372,100 resolution elements of 2× 2 arcmin 2, between dispersion measures of 170 and 675~pc~cm −3 . Based on the event rate calculations in Trott, Tingay & Wayth (2013), which assumes a standard candle luminosity of 8×10 37 Js −1 , we predict that with this choice of observational parameters, the MWA should detect (~10 ,~2 ,~0 ) FRBs with spectral indices corresponding to (− 2, − 1, 0), based on a 7σ detection threshold. We find no FRB candidates above this threshold from our search, placing an event rate limit of <700 above 700 Jy.ms per day per sky and providing evidence against spectral indices α<−1.2 (S∝ν α). We compare our event rate and spectral index limits with others from the literature. We briefly discuss these limits in light of recent suggestions that supergiant pulses from young neutron stars could explain FRBs. We find that such supergiant pulses would have to have much flatter spectra between 150 and 1400 MHz than have been observed from Crab giant pulses to be consistent with the FRB spectral index limit we derive

Histopathological alterations in Senegal sole, Solea Senegalensis, from a polluted Huelva estuary (SW, Spain)

As a component of a large research project to evaluate the effects of contaminants on fish health in the field, histopathological studies have been conducted to help establish causal relationship between pollutants (heavy metals and aromatic polycyclic hydrocarbons—PAHs) and histopathological responses in Senegal sole, Solea senegalensis, from an estuary of SW Spain. Heavy metals (As, Zn, Cd, Pb, Cu and Fe) and 16 PAHs (proprietary USEPA) concentrations in water, sediment and tissues (liver and gills) and histopathological alterations in S. senegalensis from three sampling sites of Ria de Huelva estuary during 2004–2006 years have been analysed. The histopathological studies revealed seasonal and spatial differences in the lesion grade of alterations observing the highest lesion grades in fish from Odiel River and autumn season. No significant differences were observed in the alterations prevalence between sampling sites, but significant differences were observed between seasons observing the highest prevalence in autumn season. However, calculated IPAT demonstrated a low–moderate impact of pollutants on health fish. Correlations between histopathological alterations and pollutants analysed were observed being heavy metals the group that presented a major number of correlations with alterations in several organs of S. senegalensis. In evaluating the general health of fish, the use of histopathological studies in recommended for making more reliable assessment of biochemical responses in fish exposed to a variety of environmental stressors. Statistical analysis using semiquantitative data on pathological lesions can help to establish correlation between cause (stressor) and effect (biomarker)

Microbial load on medicinal plants sold in Bini markets, Nigeria

669-672Microbiological analysis was carried out on samples of 20 medicinal plants obtained from open markets in Benin and her environs. The standard plate count technique on Nutrient agar (NA) was used to determine the total aerobic bacterial count, mannitol salt agar and Baird-Parker agar for staphylococcal count, MacConkey agar for coliform count and potato dextrose agar for fungal counts. The purified bacterial and fungal isolates were then characterized and identified. All the samples examined contained microorganisms. The bacterial count ranged from 1.0×10³ cfu/g to 9.8×10⁴ cfu/g with Aframomum meleguata, Onyokea gore and Khaya ivorensis having the highest count of 9.8 × 10⁴cfu/g; 9.4 × 10³ cfu/g and 8.8×10³ cfu/g, respectively and Justicia flava had the lowest count of 1.0 × 10³ cfu/g. The fungal counts were high in all the samples examined. The bacterial isolates were identified as Staphylococcus aureus (50.0%), Staphylococcus epidermidis (25.0%), Escherichia coli (10.0%) and Bacillus subtilis (40.0%) while fungal isolates included Aspergillus niger (85.0%) and Penicillium species (50.0%). The presence of these microorganisms in the samples could be due to improper handling and storage procedures as most of the samples were kept in bags on cold floors in very humid tropical stores (stalls)

Assessing the Level of Preparedness of Private Health Providers for Clinical Management of HIV/AIDS Epidemic in Nassarawa State, Nigeria

Very little information is available on the extent to which the private health sector is involved in clinical management of HIV/AIDS in Nigeria. This study assessed the potentials and existing capacity of 15 private health facilities in Nassarawa state for clinical management of HIV/AIDS. Information was obtained from 25 staff (15 proprietors and 10 professionals) of the randomly selected health facilities in the state using structured questionnaire. Of the 15 health facilities, three provided voluntary counselling and testing (VCT), seven had never admitted persons living with HIV/AIDS (PLWHA), two provided laboratory services, none provided home-based care for PLWHAs, two had anti-retro-viral drugs in stock, two had rooms for counselling, three had full-time doctors, and six had registered nurses. Of the 25 health workers, 5 had skills/training in conducting VCT, 15 had skills in the treatment of opportunistic infections, 14 were aware of anti-retro-viral drugs and 13 did not feel comfortable attending to PLWHAs. The study recommended capacity building on HIV/AIDS related services for the private health-workers.Evaluation du niveau de préparation des dispensateurs privés de la santé en rue du traitement clinique de l&apos;épidémie du VIH/SIDA dans l&apos;Etat de Nassarawa, Nigéria. Nous n&apos;avons que très peu de renseignement sur l&apos;étendue de l&apos;implication du secteur de la santé privé dans le traitement du VIH/SIDA au Nigéria. Cette étude a évalué le potentiel et la capacité actuelle des 15 centres médicaux dans l&apos;état de Nassarawa pour le traitement clinique du VIH/SIDA. Les renseignements ont été recueillis au sein des 25 membres de personel (15 propriétaires et 10 professionnels) de ces centres médicaux dans l&apos;état selectionnés au hazard à l&apos;aide des questionnaires structurés. De 15 établissements de santé, 3 assuraient les services de conseil et de test volontaires (CTV), 7 n&apos;ont jamais admis les personnes vivant avec le VIH/SIDA (PVVS), 2 assuraient des services de laboratoire, aucun n&apos;assurait pas de services à la maison pour les PVVS, 2 avaient en stock les médicaments antirétroviraux, 2 disposaient de salles de conseil, 3 avaient des médecins à plein temps et 6 avaient des infirmières qualifiées. De 25 membres du personnel médical, 5 avaient le savoir-faire en matière de CTV, 15 étaient habilités par rapport au traitement des infections opportunistes, 14 étaient au courant de l&apos;existence des médicaments antirétroviraux et 13 ne sentaient pas à l&apos;aise en s&apos;occupant des PVVS. L&apos;étude a préconisé le renforcement de la capacité à l&apos;égard des services liés au VIH/SIDA pour le personnel de la santé privée