The morphology of the Milky Way - I. Reconstructing CO maps from simulations in fixed potentials

PublishedJournal ArticleWe present an investigation into the morphological features of the MilkyWay.We use smoothed particle hydrodynamics (SPH) to simulate the interstellar medium (ISM) in the Milky Way under the effect of a number of different gravitational potentials representing spiral arms and bars, assuming that the Milky Way is a grand design spiral in nature. The gas is subject to ISM cooling and chemistry, enabling us to track the evolution of molecular gas. We use a 3D radiative transfer code to simulate the emission from the SPH output, allowing for the construction of synthetic longitude-velocity (l-v) emission maps as viewed from the Earth. By comparing these maps with the observed emission in CO from the Milky Way, we infer the arm/bar geometry that provides a best fit to our Galaxy. We find that it is possible to reproduce nearly all features of the l-v diagram in CO emission. There is no model, however, that satisfactorily reproduces all of the features simultaneously. Models with two arms cannot reproduce all the observed arm features, while four armed models produce too bright local emission in the inner Galaxy. Our best-fitting models favour a bar pattern speed within 50-60 km s-1 kpc-1 and an arm pattern speed of approximately 20 km s-1 kpc-1, with a bar orientation of approximately 45° and arm pitch angle between 10°-15°.We thank an anonymous referee, whose comments and suggestions improved the paper. We also thank Tom Dame for providing access to the CO longitude–velocity data. The calculations for this paper were performed on the DiRAC Complexity machine, jointly funded by STFC and the Large Facilities Capital Fund of BIS, and the University of Exeter Supercomputer, a DiRAC Facility jointly funded by STFC, the Large Facilities Capital Fund of BIS and the University of Exeter. ARP is supported by an STFC-funded post-graduate studentship. CLD acknowledges funding from the European Research Council for the FP7 ERC starting grant project LOCALSTAR. DJP is supported by a Future Fellowship funded by the Australian Research Council (FT130100034). Figures showing SPH particle density were rendered using SPLASH (Price 2007). Datasets used in this paper are available at: http://hdl.handle.net/10871/15057

Pleistocene uplift and palaeoenvironments of Macquarie Island: evidence from palaeobeaches and sedimentary deposits

Macquarie Island (54°30'S, 159°00'E) is an emergent part of the Macquarie Ridge Complex composed of ocean-floor rocks of Miocene age now 4000 m above the ocean floor. A number of landforms, including palaeobeaches now above sea level (a.s.l.)on Macquarie Island, were formed by marine erosion during uplift of the island. During the last Pleistocene period of low sea level (c. 20 ka) the island was three times larger than now. Thermoluminescence (TL) dating of two palaeobeaches indicates Pleistocene ages: 172 ± 40 ka for one at 100 m a.s.l. and 340 ± 80 ka for another at 263 m a.s.l. Matching the altitude sequence of palaeobeaches on Macquarie Island with the pattern of peaks in world sea level determined from deep sea cores allows an independent estimate of beach ages. Comparison of the altitude and sea level sequences most plausibly places the 100 m palaeobeach in Oxygen Isotope Stage 5e (130-125 ka) and the 263 m palaeobeach in Stage 9 (340-330 ka), matching reasonably with the TL dates. Other palaeobeaches at about 50 m and 170-190 m a.s.l. then correlate with high sea levels. We calculate an average rate of uplift forthe island of 0.8 mma-I . At this rate, 4000 m of Macquarie Ridge uplift would have taken about five million years and the top of the island may first have emerged some 700 to 600 ka. During the six Pleistocene glacial-interglacial cycles since then, there has been periglacial rather than glacial activity on cold uplands, but conditions suitable for vegetation of the present type persisted close to sea level

‘It’s too late’. Is it really? Considerations for amblyopia treatment in older children

In recent years, media coverage has demonstrated instances in which families of children aged 7 and older, newly diagnosed with strabismic and/or anisometropic amblyopia through community eyecare services, were told it was ‘too late’ for their child to effectively respond to conventional amblyopia treatment (occlusion or atropine penalisation). Formal guidance pertaining to binocular vision anomalies from eyecare professional bodies does not specifically make reference to a child’s age, beyond stating the importance of early diagnosis and treatment of strabismus/amblyopia. However, there have been many changes in the way we view the recovery period for amblyopia, and it is well demonstrated both within literature and clinical practice that conventional treatment can improve amblyopic eye visual acuity in children beyond the age of 7 years. The occurrence of these media described cases within the community eyecare sphere would suggest it is worthwhile revisiting the literature on the subject of amblyopia treatment in older children (aged 7+ years), to address misconceptions and place in the spotlight current considerations facing clinicians when treating newly diagnosed amblyopia within this age group. This perspective review provides an evidence-based update covering the various considerations associated with treatment of amblyopia in older children, along with recent amblyopia treatment advances that could have an impact on treatment prospects for this patient group. Considerations include the risks, benefits and efficacy of treating newly diagnosed amblyopia in older children, monitoring density of suppression to mitigate intractable diplopia risk, and recent findings regarding binocular treatments for amblyopia

The evolution and distribution of phage ST160 within Salmonella enterica serotype Typhimurium

Salmonellosis is an internationally important disease of mammals and birds. Unique epidemics in New Zealand in the recent past include two Salmonella serovars: Salmonella enterica subsp. enterica serovar Typhimurium definitive type (DT) 160 (S. Typhimurium DT160) and S. Brandenburg. Although not a major threat internationally, in New Zealand S. Typhimurium DT160 has been the most common serovar isolated from humans, and continues to cause significant losses in wildlife. We have identified DNA differences between the first New Zealand isolate of S. Typhimurium DT160 and the genome-sequenced strain, S. Typhimurium LT2. All the differences could be accounted for in one cryptic phage ST64B, and one novel P22-like phage, ST160. The majority of the ST160 genome is almost identical to phage SE1 but has two regions not found in SE1 which are identical to the P22-like phage ST64T, suggesting that ST160 evolved from SE1 via two recombination events with ST64T. All of the New Zealand isolates of DT160 were identical indicating the clonal spread of this particular Salmonella. Some overseas isolates of S. Typhimurium DT160 differed from the New Zealand strain and contained SE1 phage rather than ST160. ST160 was also identified in New Zealand isolates of S. Typhimurium DT74 and S. Typhimurium RDNC-April06 and in S. Typhimurium DT160 isolates from the USA. The emergence of S. Typhimurium DT160 as a significant pathogen in New Zealand is postulated to have occurred due to the sensitivity of the Salmonella strains to the ST160 phage when S. Typhimurium DT160 first arrived. © 2010 Cambridge University Press

Mapping and modelling the geographical distribution and environmental limits of podoconiosis in Ethiopia

BACKGROUND Ethiopia is assumed to have the highest burden of podoconiosis globally, but the geographical distribution and environmental limits and correlates are yet to be fully investigated. In this paper we use data from a nationwide survey to address these issues. METHODOLOGY Our analyses are based on data arising from the integrated mapping of podoconiosis and lymphatic filariasis (LF) conducted in 2013, supplemented by data from an earlier mapping of LF in western Ethiopia in 2008-2010. The integrated mapping used woreda (district) health offices' reports of podoconiosis and LF to guide selection of survey sites. A suite of environmental and climatic data and boosted regression tree (BRT) modelling was used to investigate environmental limits and predict the probability of podoconiosis occurrence. PRINCIPAL FINDINGS Data were available for 141,238 individuals from 1,442 communities in 775 districts from all nine regional states and two city administrations of Ethiopia. In 41.9% of surveyed districts no cases of podoconiosis were identified, with all districts in Affar, Dire Dawa, Somali and Gambella regional states lacking the disease. The disease was most common, with lymphoedema positivity rate exceeding 5%, in the central highlands of Ethiopia, in Amhara, Oromia and Southern Nations, Nationalities and Peoples regional states. BRT modelling indicated that the probability of podoconiosis occurrence increased with increasing altitude, precipitation and silt fraction of soil and decreased with population density and clay content. Based on the BRT model, we estimate that in 2010, 34.9 (95% confidence interval [CI]: 20.2-51.7) million people (i.e. 43.8%; 95% CI: 25.3-64.8% of Ethiopia's national population) lived in areas environmentally suitable for the occurrence of podoconiosis. CONCLUSIONS Podoconiosis is more widespread in Ethiopia than previously estimated, but occurs in distinct geographical regions that are tied to identifiable environmental factors. The resultant maps can be used to guide programme planning and implementation and estimate disease burden in Ethiopia. This work provides a framework with which the geographical limits of podoconiosis could be delineated at a continental scale

Clinical Psychologists’ Firearm Risk Management Perceptions and Practices

The purpose of this study was to investigate the current perceptions and practices of discussing firearm risk management with patients diagnosed with selected mental health problems. A three-wave survey was mailed to a national random sample of clinical psychologists and 339 responded (62%). The majority (78.5%) believed firearm safety issues were greater among those with mental health problems. However, the majority of clinical psychologists did not have a routine system for identifying patients with access to firearms (78.2%). Additionally, the majority (78.8%) reported they did not routinely chart or keep a record of whether patients owned or had access to firearms. About one-half (51.6%) of the clinical psychologists reported they would initiate firearm safety counseling if the patients were assessed as at risk for self-harm or harm to others. Almost half (46%) of clinical psychologists reported not receiving any information on firearm safety issues. Thus, the findings of this study suggest that a more formal role regarding anticipatory guidance on firearms is needed in the professional training of clinical psychologists

Self-inflicted penetrating eye injuries using a razor blade: Case report

<p>Abstract</p> <p>Background</p> <p>A 23 year old white male with a history of social and behavioural problems attempted to blind himself chemically, with alcohol, and mechanically, with a razor blade.</p> <p>Methods</p> <p>Observational case report of a patient who self-inflicted bilateral scleral lacerations with a razor blade, after losing his job.</p> <p>Results</p> <p>The patient sustained bilateral inferior scleral perforations, with hypotony and a right traumatic cataract. He received urgent surgical repair, and prophylactic antibiotics. There were no retinal breaks or detachments. He later underwent successful cataract surgery to the right eye.</p> <p>Conclusion</p> <p>Self-inflicted ocular injury may be possible in non-psychotic patients, as a situational response to a life event. Urgent repair can completely restore vision in some cases. Referral for psychiatric counseling is mandatory.</p

Local biases drive, but do not determine, the perception of illusory trajectories

When a dot moves horizontally across a set of tilted lines of alternating orientations, the dot appears to be moving up and down along its trajectory. This perceptual phenomenon, known as the slalom illusion, reveals a mismatch between the veridical motion signals and the subjective percept of the motion trajectory, which has not been comprehensively explained. In the present study, we investigated the empirical boundaries of the slalom illusion using psychophysical methods. The phenomenon was found to occur both under conditions of smooth pursuit eye movements and constant fixation, and to be consistently amplified by intermittently occluding the dot trajectory. When the motion direction of the dot was not constant, however, the stimulus display did not elicit the expected illusory percept. These findings confirm that a local bias towards perpendicularity at the intersection points between the dot trajectory and the tilted lines cause the illusion, but also highlight that higher-level cortical processes are involved in interpreting and amplifying the biased local motion signals into a global illusion of trajectory perception

Local biases drive, but do not determine, the perception of illusory trajectories

When a dot moves horizontally across a set of tilted lines of alternating orientations, the dot appears to be moving up and down along its trajectory. This perceptual phenomenon, known as the slalom illusion, reveals a mismatch between the veridical motion signals and the subjective percept of the motion trajectory, which has not been comprehensively explained. In the present study, we investigated the empirical boundaries of the slalom illusion using psychophysical methods. The phenomenon was found to occur both under conditions of smooth pursuit eye movements and constant fixation, and to be consistently amplified by intermittently occluding the dot trajectory. When the motion direction of the dot was not constant, however, the stimulus display did not elicit the expected illusory percept. These findings confirm that a local bias towards perpendicularity at the intersection points between the dot trajectory and the tilted lines cause the illusion, but also highlight that higher-level cortical processes are involved in interpreting and amplifying the biased local motion signals into a global illusion of trajectory perception