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Principles of KLM-style Defeasible Description Logics
No full textThe past 25 years have seen many attempts to introduce defeasible-reasoning capabilities into a description logic setting. Many, if not most, of these attempts are based on preferential extensions of description logics, with a significant number of these, in turn, following the so-called KLM approach to defeasible reasoning initially advocated for propositional logic by Kraus, Lehmann, and Magidor. Each of these attempts has its own aim of investigating particular constructions and variants of the (KLM-style) preferential approach. Hereour aim is to provide a comprehensive study of the formal foundations of preferential defeasible reasoning for description logics in the KLM tradition.We start by investigating a notion of defeasible subsumption in the spirit of defeasible conditionals as studied by Kraus, Lehmann and Magidor in the propositional case. In particular, we consider a natural and intuitivesemantics for defeasible subsumption, and investigate KLM-style syntactic properties for both preferential and rational subsumption. Our contribution includes two representation results linking our semantic constructionsto the set of preferential and rational properties considered. Besides showing that our semantics is appropriate, these results pave the way for more effective decision procedures for defeasible reasoning in description logics. Indeed, we also analyse the problem of non-monotonic reasoning in description logics at the level of entailment and present an algorithm for the computation of rational closure of a defeasible knowledge base. Importantly, our algorithm relies completely on classical entailment and shows that the computationalcomplexity of reasoning over defeasible knowledge bases is no worse than that of reasoning in the underlying classical DL ALC
Gravitational-wave constraints on the equatorial ellipticity of millisecond pulsars
No full textWe present a search for continuous gravitational waves from ve radio pulsars, comprising three recycled pulsars (PSR J0437−4715, PSR J0711−6830, and PSR J0737−3039A) and two young pulsars: the Crab pulsar (J0534+2200) and the Vela pulsar (J0835−4510). We use data from the third observing run of Advanced LIGO and Virgo combined with data from their rst and second observing runs. For the rst time we are able to match (for PSR J0437−4715) or surpass (for PSR J0711−6830) the indirect limits on gravitational-wave emission from recycled pulsars inferred from their observed spin-downs, and constrain their equatorial ellipticities to be less than 10􀀀8. For each of the ve pulsars, we perform targeted searches that assume a tight coupling between the gravitational-wave and electromagnetic signal phase evolution. We also present constraints on PSR J0711−6830, the Crab pulsar and the Vela pulsar from a search that relaxes this assumption, allowing the gravitational-wave signal to vary from the electromagnetic expectation within a narrow band of frequencies and frequency derivatives
A MeerKAT Survey of Nearby Novalike Cataclysmic Variables
No full textWe present the results of MeerKAT radio observations of eleven nearby novalike cataclysmic variables. We have detected radio emission from IM Eri, RW Sex, V3885 Sgr and V603 Aql. While RW Sex, V3885 Sgr and V603 Aql had been previously detected, this is the first reported radio detection of IM Eri. Our observations have doubled the sample of non-magnetic CVs with sensitive radio data. We observe that at our radio detection limits, a specific optical luminosity erg/s/Hz (corresponding to ) is required to produce a radio detection. We also observe that the X-ray and radio luminosities of our detected novalikes are on an extension of the power law originally proposed for non-pulsating neutron star low-mass X-ray binaries. We find no other correlations between the radio emission and emission in other wavebands or any other system parameters for the existing sample of radio-detected non-magnetic CVs. We measure in-band (0.9-1.7 GHz) radio spectral indices that are consistent with reports from earlier work. Finally, we constructed broad spectral energy distributions for our sample from published multi-wavelength data, and use them to place constraints on the mass transfer rates of these systems...
Radiation Fractionation Schedules Recommended During the COVID-19 Pandemic: A Systematic Review of the Quality of Evidence and Considerations for Future Development
No full textIntroduction Numerous publications during the COVID-19 pandemic recommended the use of hypofractionated radiotherapy. This project assessed aggregate changes in the quality of the evidence supporting these schedules, to establish a comprehensive evidence base for future reference and highlight aspects for future study. Methods and Materials Based on a systematic review of published recommendations related to dose-fractionation during the COVID-19 pandemic, twenty expert panellists assigned to fourteen disease groups named and graded the highest-quality of evidence schedule(s) used routinely for each condition and also graded all COVID-era recommended schedules. The ASTRO quality of evidence criteria were used to rank the schedules. Process-related statistics and changes in distributions of quality ratings of the highest-rated versus recommended COVID-19-era schedules were described by disease groups and for specific clinical scenarios. Results From January to May 2020 there were 54 relevant publications, including a total of 233 recommended COVID-19-adapted dose-fractionations. For site-specific curative and palliative schedules, there was a significant shift in the publishing record from established higher-quality evidence to lower-quality evidence and expert opinions for the recommended schedules (p = 0.022 and p < 0.001, respectively). For curative-intent schedules, the distribution of quality scores was essentially reversed (51.4% high-quality ‘pre-COVID’ versus 49.3% supported only by expert opinion ‘in-COVID), although there was variation in the magnitude of shifts between disease sites and among specific indications. Conclusions A large number of publications recommended hypofractionated radiotherapy schedules across all major disease sites during the COVID-19 pandemic, which were supported by a lower quality of evidence than the highest-quality routinely used dose-fractionation schedules. This work provides an evidence-based assessment of these potentially practice-changing recommendations and informs individualized decision-making and counselling of patients. These data would also support radiotherapy practices in the event of second waves or surges of the pandemic in new regions of the world
Language Evolution and Healthiness for Critical Cyber-Physical Systems
No full textIn the effort to develop critical cyber-physical systems, it is tempting to extend existing computing formalisms to include continuous behaviour. This may happen in a way that neglects elements necessary for correctly expressing continuous properties of the mathematics and correct physical properties of the real world physical system. A simple language is taken to illustrate these possibilities. Issues and risks latent in this kind of approach are identified and discussed under the umbrella of ‘healthiness conditions’. Modificationsto the language in the light of the conditions discussed are elaborated, resulting in the language CDPPP (Combined Discrete and Physical Programs in Parallel). An example air conditioning system is used to illustrate the concepts presented, and it is developed both in the original ‘unhealthy’ language and in the modified ‘healthier’ CDPPP. The formal semantics of the improved language is explored
Resolving paradoxes in IT success through IT ambidexterity: The moderating role of uncertain environments
No full textAs information technology (IT) success is both essential and elusive, researchers and practitioners are faced with an ongoing challenge to determine what IT capabilities should be developed to ensure IT success. Drawing on the paradox and ambidexterity theory, we highlight paradoxes in IT success and propose that firms manage these paradoxes by developing an IT ambidexterity capability. We hypothesize that IT ambidexterity capability enhances IT success, and that uncertain environments strengthen this relationship. Our hypotheses find support in a sample of 292 British high-tech firms. This research advances the theory for a more comprehensive understanding of the impacts of IT ambidexterity capability
Polylactide-Perylene Derivative for Blue, Biodegradable Organic Light Emitting Diodes
No full textIn this work we demonstrate, for the first time, the use of polylactic acid (PLA) as a biodegradable host matrix for the construction of the active emissive layer of organic light emitting diode (OLED) devices for potential use in bioelectronics. In this preliminary study, we report a robust synthesis of two fluorescent PLA derivatives, pyrene-PLA (AH10) and perylene–PLA (AH11). These materials were prepared by the ring opening polymerization of L-lactide with hydroxyalkyl-pyrene and -perylene derivatives using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as catalyst. OLEDs were fabricated from these materials using a simple device architecture involving a solutionprocessed single-emitting layer in the configuration ITO/PEDOT:PSS/PVK:OXD-7(35%):AH10 or AH11(20%)/TPBi/LiF/Al. The turn-on voltage for the perylene OLED at 10 cd/m2 was around 6 V and a maximum brightness of 1200 cd/m2 at 13 V. The corresponding external quantum efficiency and device current efficiency was 1.5% and 2.8 cd/A respectively. In summary, this study provides proof of principle that OLEDs that can be constructed from PLA, a readily available and renewable bio-source
Thermal properties of phase change materials reinforced with multi-dimensional carbon nanomaterials
No full textEnergy conservation is an ever-growing field of research, due to the global energy demandscontinuously escalating and the need of cleaner energy sources with a reduced carbon footprint. Topreserve resources, latent heat thermal energy storage systems, utilizing phase change materials(PCMs) are being researched due to their high heat capacities and the lack of practical thermalconductivity. This review focuses on a numerical comparison of retained enthalpy and thermalconductivity enhancement (TCE) of PCMs with additions of multi-dimensionality carbonnanofillers, that are functionalized and encapsulated, whilst trying to account for the physicalphenomena that influence the effects. Interfacial chemistry between the filler and PCM will affectfiller dispersion, composite TCE, enthalpy and stability. The thermal percolation threshold has beenexplored for 0D, 1D, 2D and 3D fillers. Assessments for the best dimensionality filler at low weightfraction have also been made. The highest TCE at low weight fractions is seen from 3D carbonnanomaterials, and at high weight fraction from unfunctionalized 2D carbon nanomaterials. Thedata gathered from many research papers has allowed the confirmation of a thermal percolationthreshold in 2D nano carbon filled PCMs. By studying the intermolecular interactions of the fillerand PCM material, the composite properties can be maximised, such as achieving a high compositeenthalpy via maximizing the degree of PCM crystallization. Therefore, this review will have use forresearchers to plan new experiments and head in a forward direction towards innovation. However,there is a need for more research in this field on the topics of 1D and 2D nanocarbon fillers at highwt%, in order to compare their effectiveness and percolation with the other dimensionality fillers.There is, also, a need for more concise and complete reporting of data by researchers in the fielddue to the complex interconnected influences of the different material properties; doing so will make reviewing and comparison more accurate and faster, allowing more conclusions to be drawnfrom further review by future researchers
Flexible Multipole Moments in Smooth Particle Mesh Ewald
No full textThe smooth particle mesh Ewald sum is extended with additional force terms that arise from so-called flexible multipolemoments. These are multipole moments (of any rank) that depend explicitly on atomic positions in some local environmentthat can be made arbitrarily large. By introducing explicit dependence on atomic positions, flexible multipolemoments are polarised by their local environment, allowing both intramolecular and intermolecular polarisation to becaptured. Multipolar torques are discussed in detail and it is shown that they arise naturally in the presented framework.Furthermore, we give details of how we validated our implementation of the flexible smooth particle mesh Ewald sumby considering two mathematical limits of the smooth particle mesh Ewald summation
The relationship between language difficulties, psychosocial difficulties, and speech-language pathology service access in the community
No full textBackground: A range of factors may impact on whether children access speech-language pathology services, beyond their communication difficulties. For instance, co-occurring psychosocial difficulties may amplify children’s observable difficulties, leading to greater access. It is important to examine such associations, because they may reflect inherent differences between children with language difficulties who access services and those who do not, indicating under-servicing for sub-groups in the community. Aims: The first aim of this study was to examine possible differences in psychosocial difficulties between children with language difficulties who did versus did not access speech-language pathology (SLP) services in the past 12 months. The second aim was to examine the unique contribution of psychosocial difficulties to service access, over and above language difficulties, common predictors of service access. Methods & Procedures: Analyses were carried out on data gathered from 808 11-year-old children who took part in the Early Language in Victoria Study (ELVS). Children were categorised as having language difficulties based on their CELF-4 Core Language Score with a cut-point of >1.25 SD below the mean. The primary outcome measure was access to speech-language pathology services in the past 12 months. Comparison and predictor variables included children’s psychosocial difficulties, language skills, relevant demographic variables (gender, caregiver education), and prior SLP access. Outcomes & Results: 42 children with language difficulties who had accessed speech-language pathology services had significantly greater psychosocial difficulties than those who had not (SDQ Total Difficulties, U = 53.00, z = -4.080, p < .001). Using binary logistic regression, a model examining child gender, caregiver education, psychosocial difficulties (internalising and externalising behaviours), language difficulties, and prior SLP access (in earlier years) was significant χ2 (8) = 137.285, p < .001, with increased externalising difficulties (OR = 1.213, p < .001), increased communication difficulties (OR = .949, p <.001), and prior SLP access (OR = 7.430, p <.001) identified as unique predictors of service access. Conclusions & Implications: The results indicate that children with language difficulties who have comorbid psychosocial difficulties are more likely to access services than those who do not. Accordingly, children with language difficulties who access clinical services may require interdisciplinary support, while children without co-morbid psychosocial difficulties may be under-referred for SLP services