The Origin of X-shaped Radio Galaxies: Clues from the Z-symmetric Secondary Lobes

Existing radio images of a few X-shaped radio galaxies reveal Z-symmetric morphologies in their weaker secondary lobes which cannot be naturally explained by either the galactic merger or radio-lobe backflow scenarios, the two dominant models for these X-shaped radio sources. We show that the merger picture can explain these morphologies provided one takes into account that, prior to the coalescence of their supermassive black holes, the smaller galaxy releases significant amounts of gas into the ISM of the dominant active galaxy. This rotating gas, whose angular momentum axis will typically not be aligned with the original jets, is likely to provide sufficient ram pressure at a distance ~10 kpc from the nucleus to bend the extant jets emerging from the central engine, thus producing a Z-symmetry in the pair of radio lobes. Once the two black holes have coalesced some 10^7 yr later, a rapid reorientation of the jets along a direction close to that of the orbital angular momentum of the swallowed galaxy relative to the primary galaxy would create the younger primary lobes of the X-shaped radio galaxy. This picture naturally explains why such sources typically have powers close to the FR I/II break. We suggest that purely Z-symmetric radio sources are often en route to coalescence and the concomitant emission of substantial gravitational radiation, while X-shaped ones have already merged and radiated.Comment: 12 pages, 1 compressed figure; accepted for publication in ApJ Letter

The spectrum and outcome of paediatric traumatic brain injury in KwaZulu-Natal Province, South Africa has not changed over the last two decades

Objectives. This retrospective review of a prospectively entered and maintained hybrid electronic trauma registry was intended to develop a comprehensive overview of traumatic brain injury (TBI) in children and adolescents and to compare it with previous audits from our local environment and from other developing world centres. All TBI patients admitted to hospital were included in this study. We reviewed the age, gender, outcomes, radiological findings and treatment of the patients.Methods. All patients aged ≤18 years old who were admitted by the Pietermaritzburg Metropolitan Trauma Service (PMTS) with TBI between December 2012 and December 2016 were included in this audit. Results. During the 4-year period under review, a total of 563 children and adolescents were treated for TBI by the PMTS.  The median age was 6.4 years and 29% (n=165) were females. The mechanism of TBI was blunt trauma in 96% (n=544) of cases, with 4% (n=19) suffering penetrating trauma. The penetrating mechanisms included impalement by a cow horn and miscellaneous injuries due to saws, axes, barbed wire, spades, stones and knives. The blunt mechanisms included falls (n=102), assaults (n=108), collapse of a building (n=28), bicycle-related injury (n=14), falling off a moving vehicle (n=280), motor vehicle accident (MVA; n=59), pedestrian vehicle accident (PVA; n=183) and animal-related injuries (n=8). There were 454 (80%) mild, 67 (12%) moderate and 42 (7%) severe cases of TBI. A total of 48 patients were admitted to the intensive care unit and 23 were admitted to the high care unit. Nine patients died.  All the deaths were in the MVA and PVA group. The spectrum of TBI as diagnosed on computed tomography scans was nonspecific cerebral contusion (n=92), depressed skull fracture (n=70), sub-arachnoid haemorrhage (n=60), extradural haemorrhage (n=41), intracerebral haemorrhage (n=19), free air (n=19), subdural haemorrhage (n=13), intraventricular haemorrhage (n=9). A total of 62 (11%) patients required surgery.Conclusion. There is a significant burden of paediatric TBI in Pietermaritzburg. The majority of TBI was related to blunt trauma and assaults were very common.  Although the short-term outcomes are good, the long-term consequences are poorly understood. Injury prevention programmes are needed to help reduce this burden of disease and a nationwide trauma registry is long overdue.

Hanging-related injury in Pietermaritzburg, South Africa

Background. Hanging is a common form of self-harm, and emergency care physicians will not infrequently be called upon to manage a survivor.Despite the relative frequency of the injury, there is a paucity of literature on the topic and the spectrum and incidence of associated injuries are poorly described.Objectives. To review experience with management of victims of hanging at a major trauma centre in South Africa.Methods. All patients treated by the Pietermaritzburg Metropolitan Trauma Service following a hanging incident between December 2012 and December 2018 were identified from the Hybrid Electronic Medical Registry. Basic demographics were recorded, and the management and outcome of each patient were noted.Results. During the 6-year period under review, a total of 154 patients were seen following a hanging incident. The mean age was 29.4 years. There were 24 females (15.6%) and 130 males (84.4%). The vast majority (n=150; 97.5%) had attempted suicide, and only 4 hangings (2.5%) were accidental. A total of 92 patients (60.9%) had consumed alcohol prior to the incident. There were 23 patients with a Glasgow Coma Score (GCS) <9 (severe traumatic brain injury (TBI)), 14 with a GCS of 9 - 12 (moderate TBI) and 117 with a GCS >12 (mild TBI). A total of 7 patients (4.5%) required intensive care unit admission, and 25 (16.2%) required intubation. The following extracranial injuries were documented on computed tomography scans: hyoid bone fractures (n=2), cervical spine fracture (n=10), mandible fracture (n=4) and oesophageal injury (n=1). Intracranial pathology was evident on 27.0% of scans, with the most common finding being global cerebral ischaemia. The mortality rate was 2.5% (4/154).Conclusions. Hanging is a common mechanism of self-harm. It is associated with significant injuries and mortality. The acute management of hanging should focus on airway protection followed by detailed imaging of the head and neck. Further work must attempt to include mortuary data on hanging.

Trauma in pregnancy at a major trauma centre in South Africa

Background. Trauma in pregnancy poses a unique challenge to clinicians. Literature on this topic is limited in South Africa (SA).Objectives. To review our institution’s experience with the management of trauma in pregnancy in a developing-world setting.Methods. This study was based at Grey’s Hospital, Pietermaritzburg, SA. All pregnant patients who were admitted to our institution following trauma between December 2012 and December 2018 were identified from the Hybrid Electronic Medical Registry (HEMR).Results. During the 6-year study period, 2 990 female patients were admitted by the Pietermaritzburg Metropolitan Trauma Service (PMTS), of whom 89 were pregnant. The mean age of these patients was 25.64 (range 17 - 43) years. The mechanism of injury was road traffic crash (RTC) in 39, stab wounds (SW) in 19, assault other than SW or gunshot wounds (GSW) in 19, GSW in 8, snake bite in 5, impalement in 1, dog bite in 1, hanging in 1, sexual assault in 1 and a single case of a patient being hit by a falling object. A subset of patients sustained >1 mechanism of injury. Thirty patients were managed operatively. The mean time of gestation was 19.16 (5 - 36) weeks. Three patients died, and there were 16 fetal deaths (including 3 lost after the mother’s death). Forty-five fetuses were recorded as surviving at discharge, while 25 fetal outcomes were not specifically recorded. There were 2 threatened miscarriages and/or patients with vaginal bleeding, 1 positive pregnancy test with no recorded outcome and no premature births as a result of trauma.Conclusions. Trauma in pregnancy is relatively uncommon and mostly due to a RTC or deliberately inflicted trauma. Fetal outcome is largely dependent on the severity of the maternal injury, with injuries requiring laparotomy leading to a high fetal mortality rate

An X-ray and Optical Investigation of the Environments Around Nearby Radio Galaxies

Investigations of the cluster environment of radio sources have not shown a correlation between radio power and degree of clustering. However, it has been demonstrated that extended X-ray luminosity and galaxy clustering do exhibit a positive correlation. This study investigates a complete sample of 25 nearby (z less than 0.06) radio galaxies which are not cataloged members of Abell clusters. The environment of these radio galaxies is studied in both the X-ray and the optical by means of the ROSAT All-Sky Survey (RASS), ROSAT pointed observations, and the Palomar optical Digitized Sky Survey (DSS). X-ray luminosities and extents are determined from the RASS, and the DSS is used to quantify the degree of clustering via the spatial two-point correlation coefficient, Bgg. Of the 25 sources, 20 are greater than sigma detections in the X-ray and 11 possessed Bgg's significantly in excess of that expected for an isolated galaxy. Adding the criterion that the X-ray emission be resolved, 10 of the radio galaxies do appear to reside in poor clusters with extended X-ray emission suggestive of the presence of an intracluster medium. Eight of these galaxies also possess high spatial correlation coefficients. Taken together, these data suggest that the radio galaxies reside in a low richness extension of the Abell clusters. The unresolved X-ray emission from the other galaxies is most likely associated with AGN phenomena. Furthermore, although the sample size is small, it appears that the environments of FR I and FR II sources differ. FR I's tend to be more frequently associated with extended X-ray emission (10 of 18), whereas FR II's are typically point sources or non-detections in the X-ray (none of the 7 sources exhibit extended X-ray emission).Comment: 28 page postscript file including figures and tables, plus one landscape table and 5 GIF figure

On the Spectral Index of Distant Radio Galaxies

The problems of using the spectral index of radio galaxies in various tests, in particular, in selecting distant radio sources are considered. The history of the question of choosing a criterion of searching for distant radio galaxies based on the spectral index is presented. For a new catalog of 2442 radio galaxies constructed from NED, SDSS, and CATS data, an analytical form of the sp ectral index.redshift relation has been determined for the first time. The spectral index.angular size and spectral index.flux density diagrams have also been constructed. Peculiarities of the distribution of sources on these diagrams are discussed.Comment: 7 pages,5 figure

Indication, from Pioneer 10/11, Galileo, and Ulysses Data, of an Apparent Anomalous, Weak, Long-Range Acceleration

Radio metric data from the Pioneer 10/11, Galileo, and Ulysses spacecraft indicate an apparent anomalous, constant, acceleration acting on the spacecraft with a magnitude $\sim 8.5\times 10^{-8}$ cm/s$^2$, directed towards the Sun. Two independent codes and physical strategies have been used to analyze the data. A number of potential causes have been ruled out. We discuss future kinematic tests and possible origins of the signal.Comment: Revtex, 4 pages and 1 figure. Minor changes for publicatio

Lessons from Love-Locks: The archaeology of a contemporary assemblage

This document is the Accepted Manuscript version. The final, definitive version of this paper has been published in Journal of Material Culture, November 2017, published by SAGE Publishing, All rights reserved.Loss of context is a challenge, if not the bane, of the ritual archaeologist’s craft. Those who research ritual frequently encounter difficulties in the interpretation of its often tantalisingly incomplete material record. Careful analysis of material remains may afford us glimpses into past ritual activity, but our often vast chronological separation from the ritual practitioners themselves prevent us from seeing the whole picture. The archaeologist engaging with structured deposits, for instance, is often forced to study ritual assemblages post-accumulation. Many nuances of its formation, therefore, may be lost in interpretation. This paper considers what insights an archaeologist could gain into the place, people, pace, and purpose of deposition by recording an accumulation of structured deposits during its formation, rather than after. To answer this, the paper will focus on a contemporary depositional practice: the love-lock. This custom involves the inscribing of names/initials onto a padlock, its attachment to a bridge or other public structure, and the deposition of the corresponding key into the water below; a ritual often enacted by a couple as a statement of their romantic commitment. Drawing on empirical data from a three-year diachronic site-specific investigation into a love-lock bridge in Manchester, UK, the author demonstrates the value of contemporary archaeology in engaging with the often enigmatic material culture of ritual accumulations.Peer reviewe