A MeerKAT view on galaxy clusters: a radio-optical study of Abell 1300 and MACS J1931.8--2634

In this paper we present results from a radio-optical study of the galaxy populations of the galaxy clusters Abell 1300 and MACS J1931.8$-$2634, a merger and a relaxed system respectively both located at $z \sim 0.3$, aimed at finding evidence of merger-induced radio emission. Radio observations are taken at 1.28 GHz with the MeerKAT interferometer during its early-stage commissioning phase, and combined with archive optical data. We generated catalogues containing 107 and 162 radio sources in the A$~$1300 and MACS J1931.8--2634 cluster fields respectively, above a 0.2 mJy threshold and within a 30~arcmin radius from the cluster centre (corresponding to 8.1 and 8.8 Mpc respectively). By cross-correlating the radio and optical catalogues, and including spectroscopic information, 9 and 6 sources were found to be cluster members and used to construct the radio luminosity functions respectively for both clusters. The comparison of the radio source catalogues between the two cluster fields leads to a marginal difference, with a $2\sigma$ statistical significance. We derived the radio luminosity function at 1.28 GHz in both clusters, in the power range $22.81 < \rm {log~P_{1.28~GHz}~(W/Hz)} < 25.95$, and obtained that in A 1300 the radio luminosity function averaged over the full radio power interval is only $3.3 \pm 1.9$ times higher than the MACS J1931.8--2634 one, suggesting no statistical difference in their probability to host nuclear radio emission. We conclude that, at least for the two clusters studied here, the role of cluster mergers in affecting the statistical properties of the radio galaxy population is negligible.Comment: 18 pages, 8 figures, MNRAS accepte

Ventrolateral Origin of Each Cycle of Rhythmic Activity Generated by the Spinal Cord of the Chick Embryo

BACKGROUND: The mechanisms responsible for generating rhythmic motor activity in the developing spinal cord of the chick embryo are poorly understood. Here we investigate whether the activity of motoneurons occurs before other neuronal populations at the beginning of each cycle of rhythmic discharge. METHODOLOGY/PRINCIPAL FINDINGS: The spatiotemporal organization of neural activity in transverse slices of the lumbosacral cord of the chick embryo (E8-E11) was investigated using intrinsic and voltage-sensitive dye (VSD) imaging. VSD signals accompanying episodes of activity comprised a rhythmic decrease in light transmission that corresponded to each cycle of electrical activity recorded from the ipsilateral ventral root. The rhythmic signals were widely synchronized across the cord face, and the largest signal amplitude was in the ventrolateral region where motoneurons are located. In unstained slices we recorded two classes of intrinsic signal. In the first, an episode of rhythmic activity was accompanied by a slow decrease in light transmission that peaked in the dorsal horn and decayed dorsoventrally. Superimposed on this signal was a much smaller rhythmic increase in transmission that was coincident with each cycle of discharge and whose amplitude and spatial distribution was similar to that of the VSD signals. At the onset of a spontaneously occurring episode and each subsequent cycle, both the intrinsic and VSD signals originated within the lateral motor column and spread medially and then dorsally. By contrast, following a dorsal root stimulus, the optical signals originated within the dorsal horn and traveled ventrally to reach the lateral motor column. CONCLUSIONS/SIGNIFICANCE: These findings suggest that motoneuron activity contributes to the initiation of each cycle of rhythmic activity, and that motoneuron and/or R-interneuron synapses are a plausible site for the activity-dependent synaptic depression that modeling studies have identified as a critical mechanism for cycling within an episode

Potent 6-desfluoro-8-methylquinolones as new lead compounds in antibacterial chemotherapy

In a furtherance of our SAR study on the C-6 position of quinolone antibacterials, a series of 6-desfluoro-8-methylquinolones were synthesized and evaluated for their in vitro antimicrobial activity. As a result of this study, compounds with strong activity against Gram-positive bacteria, including ciprofloxacin-resistant and methicillin-resistant Staphylococcus aureus, were identified. The best Gram-positive antibacterial activity was exhibited by piperidinyl derivative 6c, which was 17 times more potent than ciprofloxacin and displayed extremely high activity against Streptococcus pneumoniae with an MIC value of e0.016 íg/mL. Thus, we have shown that substituent combinations in the quinolone ring, excluding the C-6 fluorine atom, might produce powerful antibacterial agents