We present deep near-infrared $K_\textrm{s}$-band imaging for 35 of the 53 sources from the high-redshift ($z \gt 2$) radio galaxy candidate sample defined in Broderick et al. (2022, PASA, 39, e061). These images were obtained using the High-Acuity Widefield K-band Imager (HAWK-I) on the Very Large Telescope. Host galaxies are detected for 27 of the sources, with $K_\textrm{s} \approx 21.6$–23.0 mag (2$^{\prime\prime}$ diameter apertures; AB). The remaining eight targets are not detected to a median $3\unicode{x03C3}$ depth of $K_\textrm{s} \approx 23.3$ mag (2$^{\prime\prime}$ diameter apertures). We examine the radio and near-infrared flux densities of the 35 sources, comparing them to the known $z \gt 3$ powerful radio galaxies with 500-MHz radio luminosities $L_{500\,\textrm{MHz}} \gt 10^{27}$ W Hz$^{-1}$. By plotting 150-MHz flux density versus $K_\textrm{s}$-band flux density, we find that, similar to the sources from the literature, these new targets have large radio to near-infrared flux density ratios, but extending the distribution to fainter flux densities. Five of the eight HAWK-I deep non-detections have a median $3\unicode{x03C3}$ lower limit of $K_\textrm{s} \gtrsim 23.8$ mag (1$.\!^{\prime\prime}$5 diameter apertures); these five targets, along with a further source from Broderick et al. (2022, PASA, 39, e061) with a deep non-detection ($K_\textrm{s} \gtrsim 23.7$ mag; $3\unicode{x03C3}$; 2$^{\prime\prime}$ diameter aperture) in the Southern H-ATLAS Regions $K_\textrm{s}$-band Survey, are considered candidates to be ultra-high-redshift ($z \gt 5$) radio galaxies. The extreme radio to near-infrared flux density ratios ($\gt 10^5$) for these six sources are comparable to TN J0924$-$2201, GLEAM J0856$+$0223 and TGSS J1530$+$1049, the three known powerful radio galaxies at $z \gt 5$. For a selection of galaxy templates with different stellar masses, we show that $z \gtrsim 4.2$ is a plausible scenario for our ultra-high-redshift candidates if the stellar mass $M_\textrm{*} \gtrsim 10^{10.5}$ M$_\odot$. In general, the 35 targets studied have properties consistent with the previously known class of infrared-faint radio sources. We also discuss the prospects for finding more UHzRG candidates from wide and deep near-infrared surveys.

Recent higher-order explicit Runge–Kutta methods are compared with the classic fourth-order (RK4) method in long-term integration of both energy-conserving and lossy systems. By comparing quantity of function evaluations against accuracy for systems with and without known solutions, optimal methods are proposed. For a conservative system, we consider positional accuracy for Newtonian systems of two or three bodies and total angular momentum for a simplified Solar System model, over moderate astronomical timescales (tens of millions of years). For a nonconservative system, we investigate a relativistic two-body problem with gravitational wave emission. We find that methods of tenth and twelfth order consistently outperform lower-order methods for the systems considered here.

The remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a $8.31$ deg$^2$ subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1–9 GHz. We present a sample of 104 radio galaxies compiled from observations conducted by the Murchison Widefield Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). We adopt an ‘absent radio core’ criterion to identify 10 radio galaxies showing no evidence for an active nucleus. We classify these as new candidate remnant radio galaxies. Seven of these objects still display compact emitting regions within the lobes at 5.5 GHz; at this frequency the emission is short-lived, implying a recent jet switch off. On the other hand, only three show evidence of aged lobe plasma by the presence of an ultra-steep-spectrum ($\alpha<-1.2$) and a diffuse, low surface brightness radio morphology. The predominant fraction of young remnants is consistent with a rapid fading during the remnant phase. Within our sample of radio galaxies, our observations constrain the remnant fraction to $4\%\lesssim f_{\mathrm{rem}} \lesssim 10\%$; the lower limit comes from the limiting case in which all remnant candidates with hotspots are simply active radio galaxies with faint, undetected radio cores. Finally, we model the synchrotron spectrum arising from a hotspot to show they can persist for 5–10 Myr at 5.5 GHz after the jets switch of—radio emission arising from such hotspots can therefore be expected in an appreciable fraction of genuine remnants.

Introduction: Introduction: Paramedics frequently make immediate life-altering decisions with minimal clinical information. This applies to their decision to treat an unconscious patient with naloxone when the history of an opioid overdose cannot be readily established. Among patients treated by paramedics with naloxone, our objective was to compare patient demographics, treatment interventions and clinical response between patients with and without a confirmed history of an opioid overdose. Methods: Methods: This was a retrospective cohort study design of consecutive patients treated with naloxone by paramedics between January 1, 2016, and June 30, 2017. Patients were classified based on whether paramedics did or did not document a history of an opioid overdose. Baseline characteristics, treatment interventions, and response to naloxone were compared between groups. Comparisons were done using a chi-squared or Fishers exact test. Results: Results: We identified 294 patients of whom 113 (38%) did not have a confirmed history of an opioid overdose. The groups were similar in gender, bystander CPR, and bystander administration of naloxone. There were no differences in the presence of pinpoint pupils, initial oxygen saturation, initial Glasgow Coma Score (GCS), respiratory rate, or time on scene. Both patient groups were managed similarly with respect to route of naloxone administration and the use of a bag valve mask. All patients who were intubated were in the no confirmed history group (n=5; p=.003). Post naloxone there were no differences in last recorded vital signs except the no confirmed history group was less likely to achieve a GCS 10 (57% versus 89%; p<.001). The overall post-naloxone development of agitation (9%) was moderate while the need for physical/chemical restraint (2%) was low with no differences between groups. All patients were transported to the hospital. Conclusion: Conclusion: A substantial proportion of patients who received naloxone did not have a confirmed history of an opioid overdose. These patients closely resembled those with a confirmed history with respect to demographics and physical characteristics. The primary difference was a lower proportion of patients with no confirmed history who achieved a post naloxone GCS 10. Despite a moderate development of post naloxone agitation, paramedics were able to manage most of these patients without the use of physical/chemical restraints.

When a suspension of small particles is overlain by a clear fluid whose density is greater than that of the interstitial fluid, but less than that of the bulk suspension, the settling of the dense suspended particles can lead to vigorous convection in the overlying fluid. This novel situation is investigated experimentally and theoretically. A sharp interface is observed between the convecting upper region and a stagnant lower region in which there is unimpeded sedimentation at low Reynolds number. There is no transport of fluid from the upper region into the lower, though there is mixing of both buoyant fluid and entrained particles from the lower region into the upper. The interface between the two regions is found to descend at a constant velocity. Systematic laboratory measurements have determined how this velocity depends on the densities of the layers and the distributions of settling velocities of the particles. A theoretical description is developed which calculates the evolution of the density of the lower region due to differential sedimentation of polydisperse particles. Buoyancy arguments based on the calculated density profile are used to place upper and lower bounds on the amount of particle entrainment into the upper layer and on the rate of fall of the interface between the convecting and sedimenting regions. The theoretical predictions are in good agreement with the experimental observations. The analysis of the interaction between convection and sedimentation in the system considered here may be particularly relevant to the description of evolving crystal-rich layers in magma chambers and of silt-laden outflow from rivers, and has a wide range of other industrial, environmental and geological applications.