951 research outputs found

    Towards a Java Subtyping Operad

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    The subtyping relation in Java exhibits self-similarity. The self-similarity in Java subtyping is interesting and intricate due to the existence of wildcard types and, accordingly, the existence of three subtyping rules for generic types: covariant subtyping, contravariant subtyping and invariant subtyping. Supporting bounded type variables also adds to the complexity of the subtyping relation in Java and in other generic nominally-typed OO languages such as C# and Scala. In this paper we explore defining an operad to model the construction of the subtyping relation in Java and in similar generic nominally-typed OO programming languages. Operads, from category theory, are frequently used to model self-similar phenomena. The Java subtyping operad, we hope, will shed more light on understanding the type systems of generic nominally-typed OO languages.Comment: 13 page

    The effects of task type and L2 proficiency on discourse appropriacy in oral task performance

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    Conceived within the TBLT framework, the present study examined pedagogic tasks as vehicles for demonstrating L2 learners’ discourse appropriacy in oral production. Eighty ESL learners’ discourse appropriacy was measured using three pragmatically-oriented task types (complaint, refusal, and advice) across four different proficiency levels. The findings showed that, for all task types, as general proficiency increased, ratings of discourse appropriacy also increased. We found that there was a pronounced difference in discourse appropriacy between the intermediate and advanced proficiency levels, and that for learners at higher levels of proficiency, discourse appropriacy did not vary from task to task. In contrast, task type made a difference for less proficient learners in that the refusal task was particularly challenging compared with other tasks

    Dissolved noble gases and stable isotopes as tracers of preferential fluid flow along faults in the Lower Rhine Embayment, Germany

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    Groundwater in shallow unconsolidated sedimentary aquifers close to the Bornheim fault in the Lower Rhine Embayment (LRE), Germany, has relatively low ÎŽ2H and ÎŽ18O values in comparison to regional modern groundwater recharge, and 4He concentrations up to 1.7 × 10−4 cm3 (STP) g–1 ± 2.2 % which is approximately four orders of magnitude higher than expected due to solubility equilibrium with the atmosphere. Groundwater age dating based on estimated in situ production and terrigenic flux of helium provides a groundwater residence time of ∌107 years. Although fluid exchange between the deep basal aquifer system and the upper aquifer layers is generally impeded by confining clay layers and lignite, this study’s geochemical data suggest, for the first time, that deep circulating fluids penetrate shallow aquifers in the locality of fault zones, implying  that sub-vertical fluid flow occurs along faults in the LRE. However, large hydraulic-head gradients observed across many faults suggest that they act as barriers to lateral groundwater flow. Therefore, the geochemical data reported here also substantiate a conduit-barrier model of fault-zone hydrogeology in unconsolidated sedimentary deposits, as well as corroborating the concept that faults in unconsolidated aquifer systems can act as loci for hydraulic connectivity between deep and shallow aquifers. The implications of fluid flow along faults in sedimentary basins worldwide are far reaching and of particular concern for carbon capture and storage (CCS) programmes, impacts of deep shale gas recovery for shallow groundwater aquifers, and nuclear waste storage sites where fault zones could act as potential leakage pathways for hazardous fluids

    Cochlea-inspired tonotopic resonators

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    The cochlea has long been the subject of investigation in various research fields due to its intriguing spiral architecture and unique sensing characteristics. One of its most interesting features is tonotopy, the abil- ity to sense acoustic waves at different spatial locations based on their frequency content. In this work, we propose a novel design for a tonotopic resonator, based on a cochlea-inspired spiral, which can dis- criminate the frequency content of elastic waves without the use of sub-wavelength resonators. The structure is the result of an optimization process to obtain a uniform distribution of displacement max- ima along its centreline for frequencies spanning nearly two-decades, while maintaining a compact design. Numerical simulations are performed to demonstrate the concept and experimental measure- ments to validate it on a 3D printed structure. The resulting frequency-dependent distribution is also shown to be a viable means to discriminate signals with various frequency components. We also show that for appropriate parameter ranges, the tonotopic behaviour can be inverted, i.e., lower frequencies can be made to concentrate in narrower regions, as happens in the real cochlea. The harnessed tonotopic features can be used as a fundamental principle to design structures with applications in areas such as non-destructive testing and vibration attenuation

    Tiny Publics and Social Worlds—Toward a Sociology of the Local. Gary Alan Fine in Conversation With Reiner Keller

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    Gary Alan FINE gehört weltweit zu den prominentesten Persönlichkeiten der zeitgenössischen soziologischen Ethnografie. In diesem GesprĂ€ch spricht er ĂŒber EinflĂŒsse in seiner akademischen Laufbahn und prĂ€gende intellektuelle Entscheidungen. Er gilt als "serieller Ethnograf", der in zahlreichen Feldkontexten gearbeitet hat und dabei einerseits Kleingruppen und eine von Menschen bevölkerte Ethnografie favorisiert, sich andererseits mit GerĂŒchten, Klatsch und moralischen Geschichten beschĂ€ftigt, die in kleinen und grĂ¶ĂŸeren Publiken erzĂ€hlt werden. FINE beschreibt sein theoretisches Kerninteresse als die Untersuchung des Wechselspiels von Struktur, Interaktion und Kultur. In seinem Werk analysiert er die vielfĂ€ltigen ortsgebundenen Arten und Weisen, in denen Gesellschaft von Menschen in formellen und informellen sozialen Settings verwirklicht wird, angefangen bei Baseballteams ĂŒber RestaurantkĂŒchen oder die Wetterberichterstattung bis hin zum Schachspielen –um nur einige wenige GegenstĂ€nde seiner Forschungen zu nennen. Wesentlich beeinflusst durch symbolisch-interaktionistisches Denken und im Rekurs auf weitere wichtige Perspektiven auf soziale Welten plĂ€diert er fĂŒr eine selbstbewusste Haltung der ethnografischen Forschung und des ethnografischen Schreibens sowie fĂŒr die Bedeutung der Konzeptarbeit in einer theorie-informierten empirischen Soziologie dessen, was Menschen zusammen tun.Gary Alan FINE is among the most prominent figures in contemporary sociological ethnography worldwide. In this conversation, he talks about influences in his academic career and key intellectual choices. Considered to be a "serial ethnographer" who has worked in multiple settings, his work focuses on small groups and peopled ethnography, as well as on rumors, gossip, and moral story telling in tiny and larger publics. FINE describes his core theoretical interest as residing in the interplay of structure, interaction, and culture and discusses the multiple local ways society is realized by people in formal and informal social settings: ranging from baseball teams, restaurant kitchens, weather reporting to chess players—to name but a few research sites. Influenced by symbolic interactionist thinking and other important approaches to social worlds, he argues for a confident voice of ethnographic research and writing as well as the importance of conceptual work in a theory-informed empirical sociology of what people do together

    Ten Years of Experience Training Non-Physician Anesthesia Providers in Haiti.

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    Surgery is increasingly recognized as an effective means of treating a proportion of the global burden of disease, especially in resource-limited countries. Often non-physicians, such as nurses, provide the majority of anesthesia; however, their training and formal supervision is often of low priority or even non-existent. To increase the number of safe anesthesia providers in Haiti, MĂ©decins Sans FrontiĂšres has trained nurse anesthetists (NAs) for over 10 years. This article describes the challenges, outcomes, and future directions of this training program. From 1998 to 2008, 24 students graduated. Nineteen (79%) continue to work as NAs in Haiti and 5 (21%) have emigrated. In 2008, NAs were critical in providing anesthesia during a post-hurricane emergency where they performed 330 procedures. Mortality was 0.3% and not associated with lack of anesthesiologist supervision. The completion rate of this training program was high and the majority of graduates continue to work as nurse anesthetists in Haiti. Successful training requires a setting with a sufficient volume and diversity of operations, appropriate anesthesia equipment, a structured and comprehensive training program, and recognition of the training program by the national ministry of health and relevant professional bodies. Preliminary outcomes support findings elsewhere that NAs can be a safe and effective alternative where anesthesiologists are scarce. Training non-physician anesthetists is a feasible and important way to scale up surgical services resource limited settings

    Synthetic biology in society: learning from past experience?

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    Drawing an analogy to past debates over biotechnology, some stakeholders fear that synthetic biology (SB) could raise public concerns. Accordingly, ‘lessons from the past’ should be applied to avoid controversies. However, biotechnology in the 1990s is not the only possible comparator. The potential to become contested has been attributed to a number of other novel technologies. Looking at nanotechnology for example, controversies have not materialised to the extent predicted. The article discusses factors relevant for controversies over technologies as well as differences to the situation when modern biotechnology began to proliferate. Certain properties attributed to SB in the discussion so far indeed suggest a potential for controversies of its own, but perceptions may follow those on other aspects of biotechnology subject to local contingencies. Finally, it is questioned whether ELSI research should see its task in applying lessons from the past to ease technology introduction. Today, rather than seeing themselves being embedded in a linear model of technology development, social scientists take an interest in developments ‘upstream’ where technologies take shape
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