Showing papers by "City University London published in 2018"
TL;DR: This paper provides a deep learning-based strategy for reconstruction of CS-MRI, and bridges a substantial gap between conventional non-learning methods working only on data from a single image, and prior knowledge from large training data sets.
Abstract: Compressed sensing magnetic resonance imaging (CS-MRI) enables fast acquisition, which is highly desirable for numerous clinical applications. This can not only reduce the scanning cost and ease patient burden, but also potentially reduce motion artefacts and the effect of contrast washout, thus yielding better image quality. Different from parallel imaging-based fast MRI, which utilizes multiple coils to simultaneously receive MR signals, CS-MRI breaks the Nyquist–Shannon sampling barrier to reconstruct MRI images with much less required raw data. This paper provides a deep learning-based strategy for reconstruction of CS-MRI, and bridges a substantial gap between conventional non-learning methods working only on data from a single image, and prior knowledge from large training data sets. In particular, a novel conditional Generative Adversarial Networks-based model (DAGAN)-based model is proposed to reconstruct CS-MRI. In our DAGAN architecture, we have designed a refinement learning method to stabilize our U-Net based generator, which provides an end-to-end network to reduce aliasing artefacts. To better preserve texture and edges in the reconstruction, we have coupled the adversarial loss with an innovative content loss. In addition, we incorporate frequency-domain information to enforce similarity in both the image and frequency domains. We have performed comprehensive comparison studies with both conventional CS-MRI reconstruction methods and newly investigated deep learning approaches. Compared with these methods, our DAGAN method provides superior reconstruction with preserved perceptual image details. Furthermore, each image is reconstructed in about 5 ms, which is suitable for real-time processing.
835 citations
TL;DR: It is demonstrated that viscoelasticity can reduce turbulence and suppress cavitation, and subsequently increase the injector’s volumetric efficiency.
Abstract: We identify the physical mechanism through which newly developed quaternary ammonium salt (QAS) deposit control additives (DCAs) affect the rheological properties of cavitating turbulent flows, resulting in an increase in the volumetric efficiency of clean injectors fuelled with diesel or biodiesel fuels. Quaternary ammonium surfactants with appropriate counterions can be very effective in reducing the turbulent drag in aqueous solutions, however, less is known about the effect of such surfactants in oil-based solvents or in cavitating flow conditions. Small-angle neutron scattering (SANS) investigations show that in traditional DCA fuel compositions only reverse spherical micelles form, whereas reverse cylindrical micelles are detected by blending the fuel with the QAS additive. Moreover, experiments utilising X-ray micro computed tomography (micro-CT) in nozzle replicas, quantify that in cavitation regions the liquid fraction is increased in the presence of the QAS additive. Furthermore, high-flux X-ray phase contrast imaging (XPCI) measurements identify a flow stabilization effect in the region of vortex cavitation by the QAS additive. The effect of the formation of cylindrical micelles is reproduced with computational fluid dynamics (CFD) simulations by including viscoelastic characteristics for the flow. It is demonstrated that viscoelasticity can reduce turbulence and suppress cavitation, and subsequently increase the injector’s volumetric efficiency.
704 citations
University of Southern California1, University of Oslo2, Oslo University Hospital3, University of Pittsburgh4, Oxford Health NHS Foundation Trust5, University of Cape Town6, University of Texas Health Science Center at Houston7, Heidelberg University8, Neuroscience Research Australia9, Karolinska Institutet10, City University London11, King's College London12, University of Münster13, Icahn School of Medicine at Mount Sinai14, University of Barcelona15, Brown University16, French Institute of Health and Medical Research17, University of Pennsylvania18, Utrecht University19, University of Göttingen20, University of Amsterdam21, Hartford Hospital22, Yale University23, National University of Ireland, Galway24, University of São Paulo25, University of Edinburgh26, West Los Angeles College27, University of California, Los Angeles28, University of California, Irvine29, McGovern Institute for Brain Research30, Medical College of Wisconsin31, Radboud University Nijmegen32, Northumberland, Tyne and Wear NHS Foundation Trust33, National Institutes of Health34, University of California, San Diego35, Dresden University of Technology36, University of Adelaide37, Semel Institute for Neuroscience and Human Behavior38, Pasteur Institute39, University of Birmingham40, VU University Medical Center41, University of Cincinnati Academic Health Center42, University of New South Wales43, Poznan University of Medical Sciences44, Dalhousie University45, Karolinska University Hospital46, University of Gothenburg47, University of Exeter48, Janssen Pharmaceutica49, Cardiff University50
TL;DR: The largest study to date of cortical gray matter thickness and surface area measures from brain magnetic resonance imaging scans of bipolar disorder patients is performed, revealing previously undetected associations and providing an extensive analysis of potential confounding variables in neuroimaging studies of BD.
Abstract: Despite decades of research, the pathophysiology of bipolar disorder (BD) is still not well understood. Structural brain differences have been associated with BD, but results from neuroimaging studies have been inconsistent. To address this, we performed the largest study to date of cortical gray matter thickness and surface area measures from brain magnetic resonance imaging scans of 6503 individuals including 1837 unrelated adults with BD and 2582 unrelated healthy controls for group differences while also examining the effects of commonly prescribed medications, age of illness onset, history of psychosis, mood state, age and sex differences on cortical regions. In BD, cortical gray matter was thinner in frontal, temporal and parietal regions of both brain hemispheres. BD had the strongest effects on left pars opercularis (Cohen's d=-0.293; P=1.71 × 10-21), left fusiform gyrus (d=-0.288; P=8.25 × 10-21) and left rostral middle frontal cortex (d=-0.276; P=2.99 × 10-19). Longer duration of illness (after accounting for age at the time of scanning) was associated with reduced cortical thickness in frontal, medial parietal and occipital regions. We found that several commonly prescribed medications, including lithium, antiepileptic and antipsychotic treatment showed significant associations with cortical thickness and surface area, even after accounting for patients who received multiple medications. We found evidence of reduced cortical surface area associated with a history of psychosis but no associations with mood state at the time of scanning. Our analysis revealed previously undetected associations and provides an extensive analysis of potential confounding variables in neuroimaging studies of BD.
525 citations
TL;DR: This article contributes toconfigurational research by articulating how to leverage qualitative comparative analysis for enriching configurational theories of strategy and organization.
Abstract: Qualitative Comparative Analysis (QCA) is increasingly applied in strategy and organization research. The main purpose of our essay is to support this growing community of QCA scholars by identifying best practices that can help guide researchers through the key stages of a QCA empirical study (model building, sampling, calibration, data analysis, reporting and interpretation of findings) and by providing examples of such practices drawn from strategy and organization studies. Coupled with this main purpose, we respond to Miller’s (2017) essay on configuration research by highlighting our points of agreement regarding his recommendations for configurational research and by addressing some of his concerns regarding QCA. Our article thus contributes to configurational research by articulating how to leverage QCA for enriching configurational theories of strategy and organization.
383 citations
TL;DR: The results show that the theoretically predicted dynamics of critical mass do in fact emerge as expected within an empirical system of social coordination, and the existence of a tipping point in the dynamics of changing social conventions is provided.
Abstract: Theoretical models of critical mass have shown how minority groups can initiate social change dynamics in the emergence of new social conventions. Here, we study an artificial system of social conventions in which human subjects interact to establish a new coordination equilibrium. The findings provide direct empirical demonstration of the existence of a tipping point in the dynamics of changing social conventions. When minority groups reached the critical mass—that is, the critical group size for initiating social change—they were consistently able to overturn the established behavior. The size of the required critical mass is expected to vary based on theoretically identifiable features of a social setting. Our results show that the theoretically predicted dynamics of critical mass do in fact emerge as expected within an empirical system of social coordination.
346 citations
TL;DR: In this article, the authors developed and validated a new measure of corporate stakeholder responsibility (CStR), which refers to an organization's context-specific actions and policies designed to enhance the welfare of various stakeholder groups by accounting for the triple bottom line of economic, social, and environmental performance.
340 citations
TL;DR: In this paper, a holistic business model framework is developed, which is then used to analyse the empirical evidence from the creative industries, and three new themes for future research are highlighted.
262 citations
TL;DR: Dariush Mozaffarian and colleagues review strategies governments can use to improve nutrition and health and suggest several approaches that can be used to achieve this.
Abstract: Dariush Mozaffarian and colleagues review strategies governments can use to improve nutrition and health
245 citations
TL;DR: In this paper, the authors conduct face-to-face interviews with bank CEOs to classify 397 banks across 21 countries as either relationship or transaction lenders, and then use the geographic coordinates of these banks' branches and of 14,100 businesses to analyze how the lending techniques of banks in the vicinity of firms are related to credit constraints at two contrasting points of the credit cycle.
235 citations
27 Aug 2018
TL;DR: Explainable AI is not a new field but the evolution of formal reasoning architectures to incorporate principled probabilistic reasoning helped address the capture and use of uncertain knowledge.
Abstract: Explainable AI is not a new field. Since at least the early exploitation of C.S. Pierce’s abductive reasoning in expert systems of the 1980s, there were reasoning architectures to support an explanation function for complex AI systems, including applications in medical diagnosis, complex multi-component design, and reasoning about the real world. So explainability is at least as old as early AI, and a natural consequence of the design of AI systems. While early expert systems consisted of handcrafted knowledge bases that enabled reasoning over narrowly well-defined domains (e.g., INTERNIST, MYCIN), such systems had no learning capabilities and had only primitive uncertainty handling. But the evolution of formal reasoning architectures to incorporate principled probabilistic reasoning helped address the capture and use of uncertain knowledge.
220 citations
Public Health Research Institute1, University of Erlangen-Nuremberg2, University of Sydney3, VU University Amsterdam4, University College London5, University of Amsterdam6, Utrecht University7, City University London8, Middle East Technical University9, Lüneburg University10, University of New South Wales11, Karolinska Institutet12, University of Lübeck13, University of Hamburg14, University of Tokyo15, Linköping University16, Oregon Research Institute17, University of Gothenburg18, Macquarie University19, University of Southern Denmark20, University of Bergen21, St. Vincent's Health System22, University of Bern23
TL;DR: Guided Internet-based interventions lead to substantial positive treatment effects on treatment response and remission at post-treatment and may complement existing services for depression and potentially reduce the gap between the need and provision of evidence-based treatments.
TL;DR: In this article, the authors considered an optimum tuned mass damper-inerter (TMDI) design framework accommodating the above effects while accounting for parametric uncertainty to the host structure properties, modeled as a linear multi degree of freedom system, and modeled as stationary colored noise.
Abstract: The tuned mass-damper-inerter (TMDI) is a recently proposed linear passive dynamic vibration absorber for the seismic protection of buildings. It couples the classical tuned mass damper (TMD) with an inerter, a two-terminal device resisting the relative acceleration of its terminals, in judicial topologies, achieving mass-amplification and higher-modes-damping effects compared to the TMD. This paper considers an optimum TMDI design framework accommodating the above effects while accounting for parametric uncertainty to the host structure properties, modeled as a linear multi degree of freedom system, and to the seismic excitation, modeled as stationary colored noise. The inerter device constant, acting as a TMD mass amplifier, is treated as a design variable, whereas performance variables sensitive to high-frequency structural response dynamics are used to account for the TMDI influence to the higher structural modes. Reliability criteria are adopted for quantifying the structural performance, expressed through the probability of occurrence of different failure modes related to the trespassing of acceptable thresholds for the adopted performance variables: floor accelerations, interstory drifts, and attached mass displacement. The design objective function is taken as a linear combination of these probabilities following current performance-based seismic design trends. Analytical and simulation-based tools are adopted for the efficient estimation of the underlying stochastic integral defining the structural performance under uncertainty. A 10-story building under stationary Kanai-Tajimi stochastic excitation is considered to illustrate the design framework for various TMDI topologies and attached mass values. It is shown that the TMDI achieves enhanced structural performance and robustness to building and excitation uncertainties compared to same mass/weight TMDs.
TL;DR: The value spaces framework is offered as a tool for better understanding value creation and capture in digital innovation and the early contours of a research agenda for information systems researchers are illustrated.
TL;DR: The authors examines the growing prominence accorded to the idea of resilience as a regulatory ideal, locating it in the context of a "turn to character" in contemporary culture which we see as...
Abstract: This article examines the growing prominence accorded to the idea of ‘resilience’ as a regulatory ideal, locating it in the context of a ‘turn to character’ in contemporary culture which we see as ...
TL;DR: This paper provides an urgently needed framework for guiding the development of AR in an omnichannel context and synthesises current research, illustrating how a variety of current applications merge online and offline experiences.
Abstract: Purpose—This paper explores the current and future role of Augmented Reality (AR) as an enabler of omnichannel experiences across the customer journey. To advance the conceptual understanding and managerial exploitation of AR, the paper synthesises current research, illustrating how a variety of current applications merge online and offline experiences, and provides a future research agenda to help advance the state of the art in AR.
Design/methodology/approach—Drawing on situated cognition theorising as a guiding framework, the paper reviews previously published research and currently deployed applications to provide a roadmap for future research efforts on AR-enabled omnichannel experiences across the customer journey.
Findings—AR offers myriad opportunities to provide customers with a seamless omnichannel journey, smoothing current obstacles, through a unique combination of i) embedded, ii) embodied, and iii) extended customer experiences. These three principles constitute the overarching value drivers of AR and offer coherent, theory-driven organising principles for managers and researchers alike.
Originality/value—Current research has yet to provide a relevant, conceptually robust understanding of AR-enabled customer experiences. In light of the rapid development and widespread deployment of the technology, this paper provides an urgently needed framework for guiding the development of AR in an omnichannel context.
TL;DR: In this paper, the authors propose the use of social media data and sentiment analysis to study the affect-based responses to organizational actions by citizens, and critically discuss and compare the method used to measure organizational legitimacy.
Abstract: Conventional quantitative methods for the measurement of organizational legitimacy consider mainly three sources that make judgments about organizations visible: news media, accreditation bodies, and surveys Over the last decade, however, social media have enabled ordinary citizens to bypass the gatekeeping function of these institutional evaluators and autonomously make individual judgments public This inclusion of voices beyond functional and formally organized stakeholder groups potentially pluralizes the ongoing discussions about organizations The individual judgments in blogs, tweets, and Facebook posts give indication about the broader fit between an organization’s perceived behavior and heterogeneous social norms and therefore constitute an indicator of organizational legitimacy that can be accessed and measured We propose the use of social media data and sentiment analysis to study the affect-based responses to organizational actions by citizens We critically discuss and compare the method wi
TL;DR: In this paper, the authors use machine learning and AI-assisted trading to predict the short-term evolution of the cryptocurrency market and show that simple trading strategies assisted by state-of-the-art machine learning algorithms outperform standard benchmarks.
Abstract: Machine learning and AI-assisted trading have attracted growing interest for the past few years. Here, we use this approach to test the hypothesis that the inefficiency of the cryptocurrency market can be exploited to generate abnormal profits. We analyse daily data for cryptocurrencies for the period between Nov. 2015 and Apr. 2018. We show that simple trading strategies assisted by state-of-the-art machine learning algorithms outperform standard benchmarks. Our results show that nontrivial, but ultimately simple, algorithmic mechanisms can help anticipate the short-term evolution of the cryptocurrency market.
TL;DR: In this article, the authors argue that beauty apps offer a technology of gender which brings together digital self-monitoring and postfeminist modalities of subjecthood to produce an unprecedented regulatory gaze upon women, which is marked by the intensification, extensification and psychologization of surveillance.
Abstract: This article argues that ‘beauty apps’ are transforming the arena of appearance politics and foregrounds a theoretical architecture for critically understanding them. Informed by a feminist-Foucaultian framework, it argues that beauty apps offer a technology of gender which brings together digital self-monitoring and postfeminist modalities of subjecthood to produce an hitherto unprecedented regulatory gaze upon women, which is marked by the intensification, extensification and psychologization of surveillance. The article is divided into four sections. First, it introduces the literature on digital self-tracking. Second, it sets out our understanding of neoliberalism and postfeminism. Third, it looks at beauty and surveillance, before offering, in the final section, a typology of appearance apps. This is followed by a discussion of the modes of address/authority deployed in these apps – especially what we call ‘surveillant sisterhood’ – and the kinds of entrepreneurial subjectivity they constitute. The a...
TL;DR: At the group level, young people with a history of DLD more commonly have less skilled employment and more rarely achieve professional roles, and at the individual level there is considerable variation with smaller but not trivial proportions of young adults with a History of D LD showing good educational and employment outcomes.
Abstract: Background: Developmental language disorder (DLD) presents a considerable barrier for young adults to engage in further education and training. Early studies with young adults with DLD revealed poor educational achievement and lack of opportunities to progress in education. More recent studies have provided more positive findings. Relatively sparse data exist, however, on current cohorts and the factors that predict outcomes.
Aims: To examine educational and employment outcomes in young adulthood in a sample of people with histories of DLD, compared with an age-matched peer group without DLD. We ask: How do educational pathways and early jobs compare between those with and without DLD? Are young adults with DLD receiving similar levels of income as their peers? To what extent are language and literacy abilities associated with outcomes?
Methods & Procedures: Participants included 84 individuals with DLD (67% males) and 88 age-matched peers without DLD (56% males). Participants were on average 24 years of age. They completed a battery of psycholinguistic, literacy and nonverbal skills assessments. Data were also collected on educational qualifications, current educational status, extent of educational support received, employment status, history and support, as well as current income.
Outcomes & Results: Those with DLD obtained lower academic and vocational qualifications. Higher educational/vocational qualifications were associated with better language, better reading and higher PIQ. There were few differences between the two groups in terms of engagement with education but the mean age at leaving education was significantly earlier in the participants with DLD. Substantially more participants with DLD reported receiving support or dispensation from their educational institution. There was no significant difference between groups in the proportion of young people currently employed, though a higher proportion of the age-matched peers was in work full-time. Participants with DLD were much more likely to be in non-professional occupations. However, when examining pay in relation to types of occupation, the groups’ incomes were broadly comparable.
Conclusions & Implications: At the group level, young people with a history of DLD more commonly have less skilled employment and more rarely achieve professional roles. At the individual level, there is considerable variation with smaller but not trivial proportions of young adults with a history of DLD showing good educational and employment outcomes. There are positive aspects to early adult outcomes for some young people with a history of DLD.
TL;DR: The StMoMo package as discussed by the authors provides tools for fitting stochastic mortality models, assessing their goodnessof-fit and performing mortality projections, including the Lee-Carter and Cairns-Blake-Dowd models.
Abstract: In this paper we mirror the framework of generalized (non-)linear models to define the family of generalized age-period-cohort stochastic mortality models which encompasses the vast majority of stochastic mortality projection models proposed to date, including the well-known Lee-Carter and Cairns-Blake-Dowd models. We also introduce the R package StMoMo which exploits the unifying framework of the generalized age-period-cohort family to provide tools for fitting stochastic mortality models, assessing their goodnessof-fit and performing mortality projections. We illustrate some of the capabilities of the package by performing a comparison of several stochastic mortality models applied to the England and Wales population.
TL;DR: In this paper, a mesoporous and macroporous carbon composite (GBMCC) was used to generate water vapor with high efficiency using negative pressure, wind-driven, steam generation.
Abstract: High-efficiency, environment friendly, renewable energy-based methods of desalination represent attractive and potentially very powerful solutions to the long-standing problem of global water shortage. Many new laboratory-scale materials have been developed for photothermal desalination but the development of low-cost, easy-to-manufacture, and scalable materials and systems that can convert solar irradiation into exploitable thermal energy in this context is still a significant challenge. This paper presents work on a geopolymer–biomass mesoporous carbon composite (GBMCC) device with mesoporous and macroporous structures for harvesting solar energy, which is then used in a device to generate water vapor with high efficiency using negative pressure, wind-driven, steam generation. The GBMCC device gives water evaporation rates of 1.58 and 2.71 kg m−2 h−1 under 1 and 3 suns illumination, with the solar thermal conversion efficiency up to 84.95% and 67.6%, respectively. A remarkable, record high water vapor generation rate of 7.55 kg m−2 h−1 is achieved under 1 sun solar intensity at the wind speed of 3 m s−1. This is a key step forward todays efficient, sustainable and economical production of clean water from seawater or common wastewater with free solar energy.
TL;DR: This review of the empirical nutrition policy literature asks what factors generate, sustain and constrain political commitment for nutrition, how and under what circumstances and identifies 18 factors that drive commitment.
Abstract: Introduction Generating country-level political commitment will be critical to driving forward action throughout the United Nations Decade of Action on Nutrition (2016–2025). In this review of the empirical nutrition policy literature, we ask: what factors generate, sustain and constrain political commitment for nutrition, how and under what circumstances? Our aim is to inform strategic ‘commitment-building’ actions. Method We adopted a framework synthesis method and realist review protocol. An initial framework was derived from relevant theory and then populated with empirical evidence to test and modify it. Five steps were undertaken: initial theoretical framework development; search for relevant empirical literature; study selection and quality appraisal; data extraction, analysis and synthesis and framework modification. Results 75 studies were included. We identified 18 factors that drive commitment, organised into five categories: actors; institutions; political and societal contexts; knowledge, evidence and framing; and, capacities and resources. Irrespective of country-context, effective nutrition actor networks, strong leadership, civil society mobilisation, supportive political administrations, societal change and focusing events, cohesive and resonant framing, and robust data systems and available evidence were commitment drivers. Low-income and middle-income country studies also frequently reported international actors, empowered institutions, vertical coordination and capacities and resources. In upper-middle-income and high-income country studies, private sector interference frequently undermined commitment. Conclusion Political commitment is not something that simply exists or emerges accidentally; it can be created and strengthened over time through strategic action. Successfully generating commitment will likely require a core set of actions with some context-dependent adaptations. Ultimately, it will necessitate strategic actions by cohesive, resourced and strongly led nutrition actor networks that are responsive to the multifactorial, multilevel and dynamic political systems in which they operate and attempt to influence. Accelerating the formation and effectiveness of such networks over the Nutrition Decade should be a core task for all actors involved.
TL;DR: The authors discuss the move away from discussions of "sexualization" to a more critical and political register interested in a variety of ways in which sex and power intersect and discuss MeToo as an example of this shifted form of engagement.
Abstract: In this short article we will aim to do three things First, we want to use this opportunity to reflect on some of the changes we have seen in the scholarly field of gender, sexuality, and intimacy over this period, and on new emerging directions Second, we want to discuss the move away from discussions of ‘sexualization’ to a more critical and political register interested in a variety of ways in which sex and power intersect Thirdly, we will discuss MeToo as an example of this shifted form of engagement, and raise some questions about its possibilities and limitations
TL;DR: This paper proposed a systems perspective on paradox that discrimi-nates the epistemological understandings from the ontological reality of tensions. But, the focus on salient, perceived tensions impedes researchers from moving to more intricate insights into paradox, which could help address the realities of complex issues, such as wicked problems.
Abstract: Paradox theory has fundamentally changed how researchers think about organizational tensions by emphasizing their oppositions and their interdependencies. Yet, most paradox studies focus on salient, perceived tensions, ignoring latent, nested tensions and their complex interconnections. This partial view is rooted in the paradox literature focusing on the epistemological realm (actors’ perception of tensions) while disregarding the ontological realm (tensions’ underlying reality). The focus on the epistemological aspects of the tensions impedes researchers from moving to more intricate insights into paradox, which could help address the realities of complex issues, such as wicked problems. We propose a systems perspective on paradox that discrimi-nates the epistemological understandings from the ontological realities of tensions. By revealing the ontology of tensions, the underlying complexity becomes empirically interpretable. We illustrate the power of this perspective by offering two research strategies that can help researchers and organizations apprehend paradoxes grounded in systems.
21 Apr 2018
TL;DR: This work explores how the biased contents of databases, the syntactic focus of natural language processing, and the opaque nature of deep learning algorithms cause chatbots difficulty in handling race-talk.
Abstract: Why is it so hard for chatbots to talk about race? This work explores how the biased contents of databases, the syntactic focus of natural language processing, and the opaque nature of deep learning algorithms cause chatbots difficulty in handling race-talk. In each of these areas, the tensions between race and chatbots create new opportunities for people and machines. By making the abstract and disparate qualities of this problem space tangible, we can develop chatbots that are more capable of handling race-talk in its many forms. Our goal is to provide the HCI community with ways to begin addressing the question, how can chatbots handle race-talk in new and improved ways?
TL;DR: It is revealed that mobility patterns evolve significantly yet smoothly, and that the number of familiar locations an individual visits at any point is a conserved quantity with a typical size of ~25, which helps improve state-of-the-art modelling of human mobility.
Abstract: Recent seminal works on human mobility have shown that individuals constantly exploit a small set of repeatedly visited locations1–3. A concurrent study has emphasized the explorative nature of human behaviour, showing that the number of visited places grows steadily over time4–7. How to reconcile these seemingly contradicting facts remains an open question. Here, we analyse high-resolution multi-year traces of ~40,000 individuals from 4 datasets and show that this tension vanishes when the long-term evolution of mobility patterns is considered. We reveal that mobility patterns evolve significantly yet smoothly, and that the number of familiar locations an individual visits at any point is a conserved quantity with a typical size of ~25. We use this finding to improve state-of-the-art modelling of human mobility4,8. Furthermore, shifting the attention from aggregated quantities to individual behaviour, we show that the size of an individual’s set of preferred locations correlates with their number of social interactions. This result suggests a connection between the conserved quantity we identify, which as we show cannot be understood purely on the basis of time constraints, and the ‘Dunbar number’9,10 describing a cognitive upper limit to an individual’s number of social relations. We anticipate that our work will spark further research linking the study of human mobility and the cognitive and behavioural sciences. Analysing high-resolution mobility traces from almost 40,000 individuals reveals that people typically revisit a set of 25 familiar locations day-to-day, but that this set evolves over time and is proportional to the size of their social sphere.
TL;DR: In this article, the basic optical properties of a sub-wavelength-dimension silicon ridge waveguide with a 20-nm-thick Ge2Sb2Te5 (GST) top-clad layer were studied.
Abstract: Phase change materials (PCMs) combined with silicon photonics are emerging as a promising platform to realize miniature photonic devices. We study the basic optical properties of a sub-wavelength-dimension silicon ridge waveguide with a 20-nm-thick Ge2Sb2Te5 (GST) top-clad layer. Numerical simulations show that the effective index of the Si-GST hybrid waveguide varies significantly when the GST changes from the amorphous to the crystalline states. This change can be utilized to make micron-size photonic devices. To experimentally verify the effectiveness of the Si-GST hybrid waveguide on light wave manipulation, we fabricated a series of unbalanced Mach-Zehnder interferometers with one arm connected with a section of Si-GST hybrid waveguide in different lengths. The transmission spectra are measured and the complex effective indices are extracted for GST at crystalline, amorphous and intermediate phases. The experimental results overall agree well with the simulation ones. The nonvolatile property of GST makes it attractive to reduce the static power consumption. This research represents a significant step towards the realization of ultra-compact Si-GST hybrid devices that will play a key role in high-density photonic integrated circuits, opening the door to many potential applications, including optical switch, memory and logic operation.
TL;DR: Using thematic analysis, three key themes were identified: the process of understanding and accepting autism; multiple barriers to satisfaction with the diagnostic process; and inadequate post-diagnostic support provision.
Abstract: Accessing an autism diagnosis is a key milestone, both for an individual and their family. Using a qualitative methodology, the current study examined the views and experiences of ten autistic adults, ten parents of children on the autism spectrum, and ten professionals involved in autism diagnosis, all based in the United Kingdom (UK). Interviewing these 30 respondents about the diagnostic process and subsequent support options, the goal was to identify aspects of the diagnostic process that are working well, and areas in which improvements are needed. Using thematic analysis, three key themes were identified: the process of understanding and accepting autism; multiple barriers to satisfaction with the diagnostic process; and inadequate post-diagnostic support provision.
TL;DR: This short review focuses on those situations in which consensus emerges ‘spontaneously’ in the absence of centralized institutions and covers topics that include the macroscopic consequences of the different microscopic rules of behavioural contagion.
Abstract: The origin of population-scale coordination has puzzled philosophers and scientists for centuries. Recently, game theory, evolutionary approaches and complex systems science have provided quantitative insights on the mechanisms of social consensus. However, the literature is vast and widely scattered across fields, making it hard for the single researcher to navigate it. This short review aims to provide a compact overview of the main dimensions over which the debate has unfolded and to discuss some representative examples. It focuses on those situations in which consensus emerges 'spontaneously' in the absence of centralized institutions and covers topics that include the macroscopic consequences of the different microscopic rules of behavioural contagion, the role of social networks and the mechanisms that prevent the formation of a consensus or alter it after it has emerged. Special attention is devoted to the recent wave of experiments on the emergence of consensus in social systems.
Book•
24 May 2018TL;DR: A comprehensive introduction to the modular representation theory of finite groups, with an emphasis on block theory, is given in this paper, where the authors take into account classical results and concepts as well as some of the modern developments in the area.
Abstract: This is a comprehensive introduction to the modular representation theory of finite groups, with an emphasis on block theory. The two volumes take into account classical results and concepts as well as some of the modern developments in the area. Volume 1 introduces the broader context, starting with general properties of finite group algebras over commutative rings, moving on to some basics in character theory and the structure theory of algebras over complete discrete valuation rings. In Volume 2, blocks of finite group algebras over complete p-local rings take centre stage, and many key results which have not appeared in a book before are treated in detail. In order to illustrate the wide range of techniques in block theory, the book concludes with chapters classifying the source algebras of blocks with cyclic and Klein four defect groups, and relating these classifications to the open conjectures that drive block theory.