Asynchronous Stabilisation and Assembly Techniques for Additive Multigrid

Multigrid solvers are among the best solvers in the world, but once applied in the real world there are issues they must overcome. Many multigrid phases exhibit low concurrency. Mesh and matrix assembly are challenging to parallelise and introduce algorithmic latency. Dynamically adaptive codes exacerbate these issues. Multigrid codes require the computation of a cascade of matrices and dynamic adaptivity means these matrices are recomputed throughout the solve. Existing methods to compute the matrices are expensive and delay the solve. Non- trivial material parameters further increase the cost of accurate equation integration. We propose to assemble all matrix equations as stencils in a delayed element-wise fashion. Early multigrid iterations use cheap geometric approximations and more accurate updated stencil integrations are computed in parallel with the multigrid cycles. New stencil integrations are evaluated lazily and asynchronously fed to the solver once they become available. They do not delay multigrid iterations. We deploy stencil integrations as parallel tasks that are picked up by cores that would otherwise be idle. Coarse grid solves in multiplicative multigrid also exhibit limited concurrency. Small coarse mesh sizes correspond to small computational workload and require costly synchronisation steps. This acts as a bottleneck and delays solver iterations. Additive multigrid avoids this restriction, but becomes unstable for non-trivial material parameters as additive coarse grid levels tend to overcorrect. This leads to oscillations. We propose a new additive variant, adAFAC-x, with a stabilisation parameter that damps coarse grid corrections to remove oscillations. Per-level we solve an additional equation that produces an auxiliary correction. The auxiliary correction can be computed additively to the rest of the solve and uses ideas similar to smoothed aggregation multigrid to anticipate overcorrections. Pipelining techniques allow adAFAC-x to be written using single-touch semantics on a dynamically adaptive mesh

Knowledge, attitudes and practices to children with disabilities in Bhutan: a contextualized literature review

The challenges of providing education for a heterogeneous student population (in respect of gender, poverty levels, language and learning aptitude and level) have been major issues in refining Bhutanese policy and practice. These challenges are noted in respect of children with ‘special needs’ in the Bhutan Education Blueprint, 2014–24 (NSB/MoE/UNICEF, 2014), which indicated that ‘government’s initiatives to enhance educational access for children with special needs remains a formidable challenge for the education sector owing to the limited number of special schools, facilities, support services and capacity of the teachers’ (p. 26). This literature review scopes some of the key issues implied by this current situation, using the existing literature on ‘children with disabilities’ CWD from both recognized academic sources as well as the so-called ‘grey’ literature. It points to an emerging recognition of both ongoing challenges and opportunities in Bhutan which parallel those in diverse international contexts

Randomized trial comparing proactive, high-dose versus reactive, low-dose intravenous iron supplementation in hemodialysis (PIVOTAL) : Study design and baseline data

Background: Intravenous (IV) iron supplementation is a standard maintenance treatment for hemodialysis (HD) patients, but the optimum dosing regimen is unknown. Methods: PIVOTAL (Proactive IV irOn Therapy in hemodiALysis patients) is a multicenter, open-label, blinded endpoint, randomized controlled (PROBE) trial. Incident HD adults with a serum ferritin 700 μg/L and/or TSAT ≥40%) or a reactive, low-dose IV iron arm (iron sucrose administered if ferritin <200 μg/L or TSAT < 20%). We hypothesized that proactive, high-dose IV iron would be noninferior to reactive, low-dose IV iron for the primary outcome of first occurrence of nonfatal myocardial infarction (MI), nonfatal stroke, hospitalization for heart failure or death from any cause. If noninferiority is confirmed with a noninferiority limit of 1.25 for the hazard ratio of the proactive strategy relative to the reactive strategy, a test for superiority will be carried out. Secondary outcomes include infection-related endpoints, ESA dose requirements, and quality-of-life measures. As an event-driven trial, the study will continue until at least 631 primary outcome events have accrued, but the expected duration of follow-up is 2-4 years. Results: Of the 2,589 patients screened across 50 UK sites, 2,141 (83%) were randomized. At baseline, 65.3% were male, the median age was 65 years, and 79% were white. According to eligibility criteria, all patients were on ESA at screening. Prior stroke and MI were present in 8 and 9% of the cohort, respectively, and 44% of patients had diabetes at baseline. Baseline data for the randomized cohort were generally concordant with recent data from the UK Renal Registry. Conclusions: PIVOTAL will provide important information about the optimum dosing of IV iron in HD patients representative of usual clinical practice. Trial Registration: EudraCT number: 2013-002267-25.Peer reviewedFinal Published versio

Structure-based inhibitors of amyloid beta core suggest a common interface with tau.

Alzheimer's disease (AD) pathology is characterized by plaques of amyloid beta (Aβ) and neurofibrillary tangles of tau. Aβ aggregation is thought to occur at early stages of the disease, and ultimately gives way to the formation of tau tangles which track with cognitive decline in humans. Here, we report the crystal structure of an Aβ core segment determined by MicroED and in it, note characteristics of both fibrillar and oligomeric structure. Using this structure, we designed peptide-based inhibitors that reduce Aβ aggregation and toxicity of already-aggregated species. Unexpectedly, we also found that these inhibitors reduce the efficiency of Aβ-mediated tau aggregation, and moreover reduce aggregation and self-seeding of tau fibrils. The ability of these inhibitors to interfere with both Aβ and tau seeds suggests these fibrils share a common epitope, and supports the hypothesis that cross-seeding is one mechanism by which amyloid is linked to tau aggregation and could promote cognitive decline

Compressively sampling the optical transmission matrix of a multimode fibre

The measurement of the optical transmission matrix (TM) of an opaque material is an advanced form of space-variant aberration correction. Beyond imaging, TM-based methods are emerging in a range of fields, including optical communications, micro-manipulation, and computing. In many cases, the TM is very sensitive to perturbations in the configuration of the scattering medium it represents. Therefore, applications often require an up-to-the-minute characterisation of the fragile TM, typically entailing hundreds to thousands of probe measurements. Here, we explore how these measurement requirements can be relaxed using the framework of compressive sensing, in which the incorporation of prior information enables accurate estimation from fewer measurements than the dimensionality of the TM we aim to reconstruct. Examples of such priors include knowledge of a memory effect linking the input and output fields, an approximate model of the optical system, or a recent but degraded TM measurement. We demonstrate this concept by reconstructing the full-size TM of a multimode fibre supporting 754 modes at compression ratios down to ∼5% with good fidelity. We show that in this case, imaging is still possible using TMs reconstructed at compression ratios down to ∼1% (eight probe measurements). This compressive TM sampling strategy is quite general and may be applied to a variety of other scattering samples, including diffusers, thin layers of tissue, fibre optics of any refractive profile, and reflections from opaque walls. These approaches offer a route towards the measurement of high-dimensional TMs either quickly or with access to limited numbers of measurements

Influencing expert judgment: attributions of crime causality.

Purpose: The present research aimed to investigate the effects of attribution on expert clinical judgment in comparison to semi-experts and lay-people. Two research questions were addressed. Firstly, would experts be less subject to attributional manipulations, in terms of their perceived ratings of dangerousness, than would semi-experts or lay-people? Second, would experts be less subject to attributional manipulations, in terms of their assessments of offender responsibility, than would semi-experts or lay-people?Method: A 3x3x2 mixed groups design was implemented. Participants read nine crime scenarios that had been internally or externally manipulated. For each scenario, participants were asked to rate offender dangerousness, offender responsibility and the seriousness of the crime and to suggest a suitable sentence length. Targeted recruitment was employed, yielding 12 experts, 21 semi-experts and 22 lay-people. Results: Offenders were considered to be more responsible for their actions and more dangerous to others in the internal manipulations than in the external ones across all crime types and by all levels of expertise. Findings indicate that semi-experts are less subject to the influence of attributional manipulations than both experts and lay-people. Marked similarities in the pattern of expert and lay-person judgments can be observed from the present analysesConclusions: The current findings lend support to previous research in the area in that similarities between expert and lay-person judgment were observed. However, through expanding and clarifying the levels of expertise investigated, the current findings highlight the need for greater research into the distinct ‘semi-expert’ group

Investigating the Influence of Causal Attributions on Both the Worksheet and Checklist Versions of the HCR-20

Attribution theories suggest that when assessing an individual's actions, judgments are made about the cause of these behaviours and often these judgments focus on internal or external causal explanations. The current research investigated the effects of internal and external attribution on the scoring of the HCR-20 and the possibility of differences in scoring between two ways of using the HCR-20 (using the HCR-20 as a worksheet versus checklist). No differences were present in the scoring between the checklist versus worksheet. Attribution effects were present within the Historical Scale, Clinical Scale, and overall scoring of the HCR-20. Ratings were higher within the internal attribution condition than the external one, indicating that judgments made using the HCR-20 are subject to attribution effects in a similar manner as unaided violence risk assessments

Assessment of carotid artery stenosis by ultrasonography, conventional angiography, and magnetic resonance angiography: Correlation with ex vivo measurement of plaque stenosis

AbstractPurpose: Several studies have investigated the correlation between Doppler ultrasonography (DUS), angiography (CA), and magnetic resonance angiography (MRA) in the evaluation of stenosis of the carotid bifurcation. However, these studies suffer from the lack of a true control—the lesion itself—and therefore conclusions about the diagnostic accuracy of each method remain relative. To determine the absolute accuracy of these modalities, we have prospectively studied lesion size with DUS, MRA, and CA in 28 patients undergoing 31 elective carotid endarterectomies and compared the percent of carotid stenosis determined by each technique to the carotid atheroma resected en bloc.Methods: All patients were evaluated by each modality within 1 month before the thromboendarterectomy. With DUS, stenosis size was determined by standard flow criteria. For angiography and MRA, stenosis was defined as residual lumenal diameter/estimated normal arterial diameter (European Carotid Surgery Trial criteria). At surgery the carotid atheroma was removed en bloc in all patients. Patients in whom the lesion could not be removed successfully without damage were excluded from the study. Stenosis of the atheroma was determined ex vivo with high-resolution (0.03 mm3) magnetic resonance and confirmed by acrylic injection of the specimen under pressure and measurement of the atheroma wall and lumen.Results: The measurements of the ex vivo stenosis by high-resolution magnetic resonance imaging correlated closely with the size of stenosis determined by the acrylic specimen casts ( r = 0.92). By ex vivo measurement, the lesions were placed in the following size categories: 40% to 59% stenosis ( n = 2), 60% to 79% stenosis ( n = 6), 80% to 89% stenosis ( n = 7), and 90% to 99% stenosis ( n = 16).Conclusions: In general, the correlation of measurements of ex vivo stenosis with all modalities was good in these severely diseased arteries, although it was better for DUS ( r = 0.80; p < 0.001) and MRA ( r = 0.76; p < 0.001) than for CA ( r = 0.56; p < 0.05). (J VASC SURG 1995;21:82-9.

Discovery of an 86 AU Radius Debris Ring Around HD 181327

HST/NICMOS PSF-subtracted coronagraphic observations of HD 181327 have revealed the presence of a ring-like disk of circumstellar debris seen in 1.1 micron light scattered by the disk grains, surrounded by a di use outer region of lower surface brightness. The annular disk appears to be inclined by 31.7 +/- 1.6 deg from face on with the disk major axis PA at 107 +/-2 deg . The total 1.1 micron flux density of the light scattered by the disk (at 1.2" < r < 5.0") of 9.6 mJy +/- 0.8 mJy is 0.17% +/- 0.015% of the starlight. Seventy percent of the light from the scattering grains appears to be confined in a 36 AU wide annulus centered on the peak of the radial surface brightness (SB) profile 86.3 +/- 3.9 AU from the star, well beyond the characteristic radius of thermal emission estimated from IRAS and Spitzer flux densities assuming blackbody grains (~ 22 AU). The light scattered by the ring appears bilaterally symmetric, exhibits directionally preferential scattering well represented by a Henyey-Greenstein scattering phase function with g = 0.30 +/- 0.03, and has an azimuthally medianed SB at the 86.3 AU radius of peak SB of 1.00 +/- 0.07 mJy arcsec^-2. No photocentric offset is seen in the ring relative to the position of the central star. A low surface brightness diffuse halo is seen in the NICMOS image to a distance of ~ 4" Deeper 0.6 micron HST/ACS PSF-subtracted coronagraphic observations reveal a faint outer nebulosity, asymmetrically brighter to the North of the star. We discuss models of the disk and properties of its grains, from which we infer a maximum vertical scale height of 4 - 8 AU at the 87.6 AU radius of maximum surface density, and a total maximum dust mass of collisionally replenished grains with minimum grain sizes of ~ 1 micron of ~ 4 M(moon).Comment: 45 pages, 15 figures, accepted for publication in Ap