Large-Amplitude, Pair-Creating Oscillations in Pulsar and Black Hole Magnetospheres

A time-dependent model for pair creation in a pulsar magnetosphere is developed. It is argued that the parallel electric field that develops in a charge-starved region (a gap) of a pulsar magnetosphere oscillates with large amplitude. Electrons and positrons are accelerated periodically and the amplitude of the oscillations is assumed large enough to cause creation of upgoing and downgoing pairs at different phases of the oscillation. With a charge-starved initial condition, we find that the oscillations result in bursts of pair creation in which the pair density rises exponentially with time. The pair density saturates at $N_\pm\simeq E_{0}^2/(8\pi m_ec^2\Gamma_{\rm thr})$, where $E_0$ is the parallel electric field in the charge-starved initial state, and $\Gamma_{\rm thr}$ is the Lorentz factor for effec tive pair creation. The frequency of oscillations following the pair creation burst is given roughly by $\omega_{\rm osc}=eE_0/(8m_ec\Gamma_{\rm thr})$. A positive feedback keeps the system stable, such that the average pair creation rate balances the loss rate due to pairs escaping the magnetosphere.Comment: 21 pages, 6 figures, ApJ submitte

Analysis of change in patient-reported outcome measures with floor and ceiling effects using the multilevel Tobit model:a simulation study and an example from a National Joint Register using body mass index and the Oxford Hip Score

OBJECTIVES: This study has three objectives. (1) Investigate the association between body mass index (BMI) and the efficacy of primary hip replacement using a patient-reported outcome measure (PROMs) with a measurement floor and ceiling, (2) Explore the performance of different estimation methods to estimate change in PROMs score following surgery using a simulation study and real word data where data has measurement floors and ceilings and (3) Lastly, develop guidance for practising researchers on the analysis of PROMs in the presence of floor and ceiling effects. DESIGN: Simulation study and prospective national medical device register. SETTING: National Register of Joint Replacement and Medical Devices. METHODS: Using a Monte Carlo simulation study and data from a national joint replacement register (162 513 patients with pre- and post-surgery PROMs), we investigate simple approaches for the analysis of outcomes with floor and ceiling effects that are measured at two occasions: linear and Tobit regression (baseline adjusted analysis of covariance, change-score analysis, post-score analysis) in addition to linear and multilevel Tobit models. PRIMARY OUTCOME: The primary outcome of interest is change in PROMs from pre-surgery to 6 months post-surgery. RESULTS: Analysis of data with floor and ceiling effects with models that fail to account for these features induce substantial bias. Single-level Tobit models only correct for floor or ceiling effects when the exposure of interest is not associated with the baseline score. In observational data scenarios, only multilevel Tobit models are capable of providing unbiased inferences. CONCLUSIONS: Inferences from pre- post-studies that fail to account for floor and ceiling effects may induce spurious associations with substantial risk of bias. Multilevel Tobit models indicate the efficacy of total hip replacement is independent of BMI. Restricting access to total hip replacement based on a patients BMI can not be supported by the data

Provision of powered communication aids in the United Kingdom

AAC service provision in the United Kingdom (UK) has evolved since the first service dedicated to the provision of communication aids opened in 1986. Within the UK, many health and care services are provided via government funding; however, the assessment and provision of AAC and specifically of speech-generating devices (SGDs) is inconsistent and inequitable. The study reported in this paper aimed to collect information on levels of current provision of powered communication aids (the term used in the study to refer to SGDs) by UK service providers in 2013 with the intention of improving future estimates for need of services. A questionnaire survey was designed and data were obtained from 98 AAC services across the UK. Service providers reported the number of individuals known to be using powered communication aids and the mean value reported was 0.0155% of the services? catchment populations. However levels of service provision reported were highly variable. Although the data reported must be treated with caution, it adds to the sparse literature on the topic, informs AAC service design and delivery in the UK, and acts as an indicative baseline measure for future service development

Volume 42, Number 4, December 2022 OLAC Newsletter

Digitized December 2022 issue of the OLAC Newsletter

Volume 43, Number 1, March 2023 OLAC Newsletter

Digitized March 2023 issue of the OLAC Newsletter

Miscellaneous personal letters of Alex Lachlan Williams, 1894-1897

Miscellaneous personal letters from Geoffrey J. Judge of Zeehan in regard to repairs to T. Gibbins' shop, lack of mining jobs and mines "commencing to look up" dated 1 July and 19 August 1894. From James Duncan regarding the tenancy of Williams' property at Zeehan dated 12 September 1896. From Ada Proctor of Sandy Bay on hearing ALW was about to leave Hobart to thank him for all he did for her Aunt dated 29 August 1897. From E.A Lorkin of North Lyell regarding the lease, amalgamation, and section not complying with labour clause written on 18 October 1897. From J. McDonald of Strahan, correspondence regarding mill timber and accompanying list of measurements of logs dated 6 September 1897. These personal letters of Alex Lachlan Williams 1894-1897 are from the papers of Oscar Jones, solicitor of Murdoch & Jones Queenstown branch and his predecessor Alex Lachlan Williams, apparently found at Strathelie at Broadmarsh formerly the Jones family home. The Queenstown practice was established by Alex Lachlan Williams in 1896. Later Charles Page became a partner and established an office at Zeehan. George Murdoch of the Stone Buildings, Hobart, later Murdoch and Jones, acted as Hobart agent and early in 1898 the two firms merged as Williams and Page of Hobart, Queenstown and Zeehan. In April 1899, however, Williams sold out to Murdoch and Jones, Oscar Jones managed the Queenstown branch and by July the firm's name was changed to Murdoch & Jones. Williams & Page remained in Zeehan, under C.S. Page. Private Deposit Collection M14/13 1-

Low Raman-noise correlated photon-pair generation in a dispersion-engineered chalcogenide As2S3 planar waveguide

We demonstrate low Raman-noise correlated photon-pair generation in a dispersion-engineered 10 mm As2S3 chalcogenide waveguide at room temperature. We show a coincidence-to-accidental ratio (CAR) of 16.8, a 250 times increase compared with previously published results in a chalcogenide waveguide, with a corresponding brightness of 3×105  pairs·s−1·nm−1 generated at the chip. Dispersion engineering of our waveguide enables photon passbands to be placed in the low spontaneous Raman scattering (SpRS) window at 7.4 THz detuning from the pump. This Letter shows the potential for As2S3 chalcogenide to be used for nonlinear quantum photonic devices.This work was supported by the Centre of Excellence, Federation Fellowship, and Discovery Early Career Researcher Award (DECRA) programs of the Australian Research Council (ARC). The Centre for Ultrahigh bandwidth Devices for Optical Systems (CUDOS) is an ARC Centre of Excellence (project number CE110001018)

Case Reports1. A Late Presentation of Loeys-Dietz Syndrome: Beware of TGFβ Receptor Mutations in Benign Joint Hypermobility

Background: Thoracic aortic aneurysms (TAA) and dissections are not uncommon causes of sudden death in young adults. Loeys-Dietz syndrome (LDS) is a rare, recently described, autosomal dominant, connective tissue disease characterized by aggressive arterial aneurysms, resulting from mutations in the transforming growth factor beta (TGFβ) receptor genes TGFBR1 and TGFBR2. Mean age at death is 26.1 years, most often due to aortic dissection. We report an unusually late presentation of LDS, diagnosed following elective surgery in a female with a long history of joint hypermobility. Methods: A 51-year-old Caucasian lady complained of chest pain and headache following a dural leak from spinal anaesthesia for an elective ankle arthroscopy. CT scan and echocardiography demonstrated a dilated aortic root and significant aortic regurgitation. MRA demonstrated aortic tortuosity, an infrarenal aortic aneurysm and aneurysms in the left renal and right internal mammary arteries. She underwent aortic root repair and aortic valve replacement. She had a background of long-standing joint pains secondary to hypermobility, easy bruising, unusual fracture susceptibility and mild bronchiectasis. She had one healthy child age 32, after which she suffered a uterine prolapse. Examination revealed mild Marfanoid features. Uvula, skin and ophthalmological examination was normal. Results: Fibrillin-1 testing for Marfan syndrome (MFS) was negative. Detection of a c.1270G > C (p.Gly424Arg) TGFBR2 mutation confirmed the diagnosis of LDS. Losartan was started for vascular protection. Conclusions: LDS is a severe inherited vasculopathy that usually presents in childhood. It is characterized by aortic root dilatation and ascending aneurysms. There is a higher risk of aortic dissection compared with MFS. Clinical features overlap with MFS and Ehlers Danlos syndrome Type IV, but differentiating dysmorphogenic features include ocular hypertelorism, bifid uvula and cleft palate. Echocardiography and MRA or CT scanning from head to pelvis is recommended to establish the extent of vascular involvement. Management involves early surgical intervention, including early valve-sparing aortic root replacement, genetic counselling and close monitoring in pregnancy. Despite being caused by loss of function mutations in either TGFβ receptor, paradoxical activation of TGFβ signalling is seen, suggesting that TGFβ antagonism may confer disease modifying effects similar to those observed in MFS. TGFβ antagonism can be achieved with angiotensin antagonists, such as Losartan, which is able to delay aortic aneurysm development in preclinical models and in patients with MFS. Our case emphasizes the importance of timely recognition of vasculopathy syndromes in patients with hypermobility and the need for early surgical intervention. It also highlights their heterogeneity and the potential for late presentation. Disclosures: The authors have declared no conflicts of interes