Simulations of an energy dechirper based on dielectric lined waveguides

Terahertz frequency wakefields can be excited by ultra-short relativistic electron bunches travelling through dielectric lined waveguide (DLW) structures. These wakefields can either accelerate a witness bunch with high gradient, or modulate the energy of the driving bunch. In this paper, we study a passive dechirper based on the DLW to compensate the correlated energy spread of the bunches accelerated by the laser plasma wakefield accelerator (LWFA). A rectangular waveguide structure was employed taking advantage of its continuously tunable gap during operation. The assumed 200 MeV driving bunch had a Gaussian distribution with a bunch length of 3.0 {\mu}m, a relative correlated energy spread of 1%, and a total charge of 10 pC. Both of the CST Wakefield Solver and PIC Solver were used to simulate and optimize such a dechirper. Effect of the time-dependent self-wake on the driving bunch was analyzed in terms of the energy modulation and the transverse phase space

Repeatability and Reproducibility of Macular Thickness Measurements Using Fourier Domain Optical Coherence Tomography

Aim: To evaluate repeatability and reproducibility of macular thickness measurements in visually normal eyes using the Topcon 3D OCT-1000. Methods: Phase 1 investigated scan repeatability, the effect of age and pupil dilation. Two groups (6 younger and 6 older participants) had one eye scanned 5 times pre and post- dilation by 1 operator. Phase 2 investigated between-operator, within and between-visit reproducibility. 10 participants had 1 un-dilated eye scanned 3 times on 2 separate visits by 2 operators. Results: Phase 1: No significant difference existed between repeat scans (p=0.75) and no significant difference was found pre- and post-dilation (p=0.54). In the younger group variation was low (95% limits ± 3.62 m) and comparable across all retinal regions. The older group demonstrated greater variation (95% limits ± 7.6 m). Phase 2: For a given retinal location, 95% confidence limits for within-operator, within-visit reproducibility was 5.16 m. This value increased to 5.56 m for the same operator over two visits and to 6.18 m for two operators over two visits. Conclusion: A high level repeatability, close to 6 m, of macular thickness measurement is possible using the 3D OCT- 1000. Measured differences in macular thickness between successive visits that exceed 6 m in pre-presbyopic individuals are therefore likely to reflect actual structural change. OCT measures are more variable in older individuals and it is advisable to take a series of scans so that outliers can be more easily identified

Exploring the concept of pain of Australian children with and without pain: Qualitative study

© 2019 Author(s). Objective A person's concept of pain can be defined as how they understand what pain actually is, what function it serves and what biological processes are thought to underpin it. This study aimed to explore the concept of pain in children with and without persistent pain. Design In-depth, face-to-face interviews with drawing tasks were conducted with 16 children (aged 8-12 years) in New South Wales, Australia. Thematic analysis was used to analyse and synthesise the data. Setting Children with persistent pain were identified from a pain clinic waiting list in Australia, and children without pain were identified through advertising flyers and email bulletins at a university and hospital. Participants Eight children had persistent pain and eight children were pain free. Results Four themes emerged from the data: â € my pain-related knowledge', â € pain in the world around me', â € pain in me' and â € communicating my concept of pain'. A conceptual framework of the potential interactions between the themes resulting from the analysis is proposed. The concept of pain of Australian children aged 8-12 years varied depending on their knowledge, experiences and literacy levels. For example, when undertaking a drawing task, children with persistent pain tended to draw emotional elements to describe pain, whereas children who were pain free did not. Conclusions Gaining an in-depth understanding of a child's previous pain-related experiences and knowledge is important to facilitate clear and meaningful pain science education. The use of age-appropriate language, in combination with appropriate assessment and education tasks such as drawing and discussing vignettes, allowed children to communicate their individual concept of pain

Prehension of a flanked target in individuals with amblyopia.

yesPurpose: Reduced binocularity is a prominent feature of amblyopia and binocular cues are thought to be important for prehension. We examine prehension in individuals with amblyopia when the target-object was flanked, thus mimicking everyday prehension. Methods: amblyopes (n=20, 36.4±11.7 years; 6 anisometropic, 3 strabismic, 11 mixed) and visually-normal controls (n=20, 27.5±6.3 years) reached forward, grasped and lifted a cylindrical target-object that was flanked with objects on either (lateral) side of the target, or in front and behind it in depth. Only 6 amblyopes (30%) had measurable stereoacuity. Trials were completed in binocular and monocular viewing, using the better eye in amblyopic participants. Results: Compared to visual normals, amblyopes displayed a longer overall movement time (p=0.031), lower average reach velocity (p=0.021), smaller maximum aperture (p=0.007) and longer durations between object contact and lift (p=0.003). Differences between groups were more apparent when the flankers were in front and behind, compared to either side, as evidenced by significant group-by-flanker configuration interactions for reach duration (p<0.001), size and timing of maximum aperture (p≤0.009), end-of-reach to object-contact (p<0.001), and between object contact and lift (p=0.044), suggesting that deficits are greatest when binocular cues are richest. Both groups demonstrated a significant binocular advantage, in that in both groups performance was worse for monocular compared to binocular viewing, but interestingly, amblyopic deficits in binocular viewing largely persisted during monocular viewing with the better eye. Conclusions: These results suggest that amblyopes either display considerable residual binocularity or that they have adapted to make good use of their abnormal binocularity

Development of longitudinal beam profile monitor based on Coherent Transition Radiation effect for CLARA accelerator

Coherent Transition Radiation (CTR) has widely been used for longitudinal beam profile diagnostics. Its spectral-spatial properties have been thoroughly theoretically and experimentally investigated. We have decided to develop a longitudinal beam profile diagnostics based on CTR technique to be used for interpreting the experimental results of Dielectric Wakefield Accelerator (DWA) and Coherent Cherenkov Diffraction Radiation (CChDR) experiments. In this paper we present the technical design,tuning and commissioning of the CTR longitudinal bunch profile monitor at CLARA facilit

Are UK policies and practices for regulated donor insemination forcing women to find unregulated sperm donors online? A perspective on the available evidence

In recent years, there has been an increase in women obtaining donor sperm via unregulated websites and social media. In this article, we bring together the disparate evidence in this emerging field to consider whether restrictive UK policies and practices for regulated clinical donor insemination (DI) are a potential explanation for the growing use of the currently unregulated, online route to donor insemination. To this end, we examine the nature of the National Institute for Health and Care Excellence (NICE) guidelines, recent data provided by the Human Fertilisation and Embryology Authority (HFEA), and prior research on who uses online sperm donation and their reasons for doing so. In addition, we highlight why this issue is important by outlining some of the benefits and drawbacks of the unregulated route. We argue that, whilst there are many factors driving the unregulated route to DI, restrictive UK policies and practices for regulated DI might be one of these. We conclude that turning our attention to structural barriers, such as regulated DI policies and practices, is necessary to produce more definitive evidence of this potential issue, and that adopting a Reproductive Justice framework could lead to more equitable provision of regulated DI services