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Polyhedral Properties of RLT Relaxations of Nonconvex Quadratic Programs and Their Implications on Exact Relaxations
Get PDFWe study linear programming relaxations of nonconvex quadratic programs given by the reformulation-linearization technique (RLT), referred to as RLT relaxations. We investigate the relations between the polyhedral properties of the feasible regions of a quadratic program and its RLT relaxation. We establish various connections between recession directions, boundedness, and vertices of the two feasible regions. Using these properties, we present necessary and sufficient exactness conditions for RLT relaxations. We then give a thorough discussion of how our results can be converted into simple algorithmic procedures to construct instances of quadratic programs with exact, inexact, or unbounded RLT relaxations
Parental beliefs towards the inclusion of autistic children in mainstream schools
Get PDFResearch has examined teacher attitudes, knowledge, and stigma towards inclusion of autistic children in mainstream schools. Less focus has been given to these beliefs among parents. This is problematic as parents are important in the implementation of inclusion and fostering a positive school environment. The current study examined differences in autism attitudes, knowledge, stigma, and inclusive education attitudes (core perspective; expected outcomes; classroom practices) among parents with and without an autistic child; The study also investigated whether autism knowledge, attitudes and stigma predicted inclusion attitudes. 185 parents in the UK (52% had an autistic child) completed questionnaires measuring these variables. Parents of an autistic child had significantly higher core perspective inclusive attitudes than parents without an autistic child. However, this group also reported more beliefs that parents of autistic children are stigmatised. For all parents, core perspective inclusive attitudes were predicted by autism attitudes and stigma towards parents of autistic children. Predictors of expected outcomes and classroom practices inclusive attitudes differed between groups. Findings highlight the need for parental attitude research to be disability-specific and consider different aspects of inclusive attitudes. Parent education to enhance inclusive attitudes should be tailored for distinct parent groups and contact interventions should be considered
The problem of disinformation:A critical approach
Get PDFThe term disinformation is generally used to refer to information that is false and harmful, by contrast with misinformation (false but harmless) and malinformation (harmful but true); disinformation is also generally understood to involve coordination and to be intentionally false and/or harmful. However, particular studies rarely apply all these criteria when discussing cases. Doing so would involve applying at least three distinct problem framings: an epistemic framing to detect that a proposition in circulation is false, a behavioural framing to detect the coordinated efforts at communicating that proposition, and a security framing to identify threats or risks of harm attendant on widespread belief in the proposition. As for the question of intentionality, different kinds of clues can be picked up within each framing, although none alone is likely to be conclusive. Yet particular studies tend to centre on or prioritise a single framing. Many today aim to make policy recommendations about combatting disinformation, and they prioritise security concerns over the demands of epistemic diligence. This carries a real risk of disinformation research being ‘weaponised’ against inconvenient truths. Against combative approaches, this article argues for a critical approach which recognizes the importance of epistemic diligence and transparency about normative assumptions.</p
What We Can Learn About Mars from the Magnetism of Returned Samples
Get PDFThe Red Planet is a magnetic planet. The Martian crust contains strong magnetization from a core dynamo that likely was active during the Noachian period when the surface may have been habitable. The evolution of the dynamo may have played a central role in the evolution of the early atmosphere and the planet’s transition to the current cold and dry state. However, the nature and history of the dynamo and crustal magnetization are poorly understood given the lack of well-preserved, oriented, ancient samples with geologic context available for laboratory study. Here, we describe how magnetic measurements of returned samples could transform our understanding of six key unknowns about Mars’ planetary evolution and habitability. Such measurements could i) determine the history of the Martian dynamo field’s intensity; ii) determine the history of the Martian dynamo field’s direction; iii) test the hypothesis that Mars experienced plate tectonics or true polar wander; iv) constrain the thermal and aqueous alteration history of the samples; v) identify sources of Martian crustal magnetization and vi) characterize sedimentary and magmatic processes on Mars. We discuss how these goals can be achieved using future laboratory analyses of samples acquired by the Perseverance rover
A Digital Tool for Clinical Evidence-Driven Guideline Development:Studying Properties of Trial Eligible and Ineligible Populations
Get PDFBackground: Clinical guideline development preferentially relies on evidence from randomisedcontrolled trials (RCTs). RCTs are the gold-standard method to evaluate the efficacy of treatments with the highest internal validity but limited external validity, in the sense that their findings may not always be applicable to or generalisable to clinical populations/population characteristics. The external validity of RCTs for the clinical population is constrained by the lack of tailored epidemiological data analysis designed for this purpose due to data governance, consistency of disease/condition definitions, re-duplicated effort in analysis code, etc.Objective: To develop a digital tool that characterises the overall population and differences between clinical trial eligible and ineligible populations from the clinical populations of a disease/condition regarding demography (in terms of groupings for e.g., age, sex, ethnicity), comorbidity, co-prescription, hospitalisation and mortality. Currently, the process is complex, onerous, and time-consuming, whereas a real-time tool may be used to rapidly inform a guideline developer’s judgement about the applicability of evidence.Methods: The National Institute for Health and Care Excellence (NICE) – particularly the gout guideline development group - and the Scottish Intercollegiate Guidelines Network (SIGN) guideline developers were consulted to gather their requirements and evidential data needs when developing guidelines. An R shiny tool was designed and developed using electronic primary healthcare data linked with hospitalisation and mortality data built upon an optimised data architecture. Disclosure control mechanisms were built into the tool to ensure data confidentiality. The tool was deployed within the Trusted Research Environment (TRE), allowing only trusted pre-approved researchers to conduct analysis.Results: The tool supports 128 chronic health conditions as index conditions and 161 conditions as comorbidities (33 in addition to the 128 index conditions). It enables two types of analyses via the graphic interface: overall population and stratified by user-defined eligibility criteria. The analyses produce overview statistical tables(on, e.g., age, gender) of the index condition population and, within the overview groupings, produce details on e.g., electronic Frailty Index (eFI), comorbidities, and co-prescriptions. The disclosure control mechanism is integral to the tool, limiting tabular counts to meet local governance needs. An exemplary result for gout as an index condition is presented to demonstrate the tool's functionality. Guideline developers from NICE and SIGN provided positive feedback on the tool.Discussion: The tool is a proof-of-concept, and the user feedback has demonstrated that this is a step towards computer interpretable guideline development.Conclusions: Using the digital tool can potentially improve evidence-driven guideline development through the availability of real-world data in real time.Keywords: Multimorbidity, clinical practice guideline, gout, Trusted Research Environment (TRE), National Institute for Health and Care Excellence (NICE), Scottish Intercollegiate Guidelines Network (SIGN
Proteomic analysis reveals dysregulation of peripheral blood neutrophils in patients with Multiple Sclerosis
Get PDFMultiple Sclerosis (MS) is a complex auto-inflammatory disease affecting the brain and spinal cord, which results in axonal de-myelination and symptoms including fatigue, pain, and difficulties with vision and mobility. The involvement of the immune system in the pathology of MS is well established, particularly the adaptive T cell response, and there has been a particular focus on the IL-17-producing subset of Th17 cells and their role in driving disease. However, the importance of innate immune cells has not been so well characterized. Here we focussed on neutrophils, which are innate immune cells and rapid responders to inflammation, and which have recently been linked to other chronic autoimmune conditions. Multiple strands of evidence in patients with MS and in mice with the experimental autoimmune encephalomyelitis MS model suggest neutrophils may play a role in driving MS inflammation. Here, we performed proteomic analysis on neutrophils from patients with MS and healthy donors, revealing striking differences. In particular, granule proteins were significantly more abundant in the MS neutrophils compared to the healthy controls, with a particular overabundance of proteins in primary and secondary granules. In addition, members of the MAVS signalling pathway were differently regulated compared to healthy donor cells. Finally, we find that MS neutrophils do not suppress T cell activation equivalently to healthy neutrophils, and in particular are unable to suppress expression of CD161 on the T cells, indicative of a suppression of Th17 differentiation. We propose that neutrophil dysregulation in MS may contribute to dysfunctional T cell responses.</p
Arab feminist cyber activism:Theorising indigenous knowledge production and decolonising feminism
Get PDFThere is a need to situate current iterations of Arabic feminist cyber activism within the long history of feminist activism in the region and to read them as initiatives in/from the margin that adopt an intersectional approach with an explicit focus on indigenous decolonial knowledge. Some Arab feminist collectives active today are producing and enabling the production of distinctly indigenous articulations of feminism situated in opposition to what can be termed hegemonic feminism, embodied in international and non-governmental women’s organizations. I analyse these collectives’ works on two levels: the level of feminist positioning and the level of mediated activism. This article argues that these collectives’ interventions are authentic and of the region, embody resistance from the margin, as well as the ethos and politics of solidarity, particularly considering their positioning on Palestine, and they resist digital colonialism through abstaining from extractive media practices and adopting a redistributive ethos
Humeral head-split fracture in two dogs
Get PDFTwo skeletally immature female dogs were each investigated for chronic weight-bearing thoracic limb lameness. The first patient was lame for 2 months following a tumble whilst playing, and the second patient had been intermittently lame since 3 weeks of age. In both cases, radiographic examination of the shoulder revealed fissuring of the caudal humeral head consistent with an incomplete proximal humeral Salter-Harris type IV fracture with an Enoki-mushroom-like appearance of the caudal fragment, where two heads rise from a common stem. There was secondary neoarthrosis of the caudal humeral head fragment with the glenoid rim of the scapula. Humeral head-split fracture is an unusual fracture pattern that rarely occurs in skeletally immature patients, and conservative management appears to result in reasonable short-term outcomes. The role of early detection and surgical intervention remains unknown.</p
On the scalability of truss geometry and topology optimization with global stability constraints via chordal decomposition
Get PDFGeometry optimization was recently introduced to existing truss topology optimization with global stability constraints. The resulting problems are formulated as highly nonlinear semidefinite programming problems that demand extensive computational effort to solve and have been solved only for small problem instances. The main challenge for effective computation is the positive semidefinite constraints which involve large sparse matrices. In this paper, we apply several techniques to tackle the challenge. First, we use the well-known chordal decomposition approach to replace each positive semidefinite constraint on a large sparse matrix by several positive semidefinite constraints on smaller submatrices together with suitable linking constraints. Moreover, we further improve the efficiency of the decomposition by applying a graph-based clique merging strategy to combine submatrices with significant overlap. Next, we couple these techniques with an optimization algorithm that fully exploits the structure of the smaller submatrices. As a result, we can solve much larger problems, which allows us to extend the existing single-load case to the multiple-load case, and to provide a computationally tractable approach for the latter case. Finally, we employ adaptive strategies from previous studies to solve successive problem instances, enabling the joints to navigate larger regions, and ultimately obtain further improved designs. The efficiency of the overall approach is demonstrated via computational experiments on large problem instances
On the importance of considering concurrent effects in random-intercept cross-lagged panel modelling:Example analysis of bullying and internalising problems
Get PDFRandom-intercept cross-lagged panel models (RI-CLPMs) are increasingly used to investigate research questions focusing on how one variable at one time point affects another variable at the subsequent time point. Due to the implied temporal sequence of events in such research designs, interpretations of RI-CLPMs primarily focus on longitudinal cross-lagged paths while disregarding concurrent associations and modeling these only as residual covariances. However, this may cause biased cross-lagged effects. This may be especially so when data collected at the same time point refers to different reference timeframes, creating a temporal sequence of events for constructs measured concurrently. To examine this issue, we conducted a series of empirical analyses in which the impact of modeling or not modeling of directional within-time point associations may impact inferences drawn from RI-CLPMs using data from the longitudinal z-proso study. Results highlight that not considering directional concurrent effects may lead to biased cross-lagged effects. Thus, it is essential to carefully consider potential directional concurrent effects when choosing models to analyze directional associations between variables over time. If temporal sequences of concurrent effects cannot be clearly established, testing multiple models and drawing conclusions based on the robustness of effects across all models is recommended
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