62 research outputs found

    Q-Strategy: A Bidding Strategy for Market-Based Allocation of Grid Services

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    The application of autonomous agents by the provisioning and usage of computational services is an attractive research field. Various methods and technologies in the area of artificial intelligence, statistics and economics are playing together to achieve i) autonomic service provisioning and usage of Grid services, to invent ii) competitive bidding strategies for widely used market mechanisms and to iii) incentivize consumers and providers to use such market-based systems. The contributions of the paper are threefold. First, we present a bidding agent framework for implementing artificial bidding agents, supporting consumers and providers in technical and economic preference elicitation as well as automated bid generation by the requesting and provisioning of Grid services. Secondly, we introduce a novel consumer-side bidding strategy, which enables a goal-oriented and strategic behavior by the generation and submission of consumer service requests and selection of provider offers. Thirdly, we evaluate and compare the Q-strategy, implemented within the presented framework, against the Truth-Telling bidding strategy in three mechanisms – a centralized CDA, a decentralized on-line machine scheduling and a FIFO-scheduling mechanisms

    Temperate infection in a virus–host system previously known for virulent dynamics

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    The blooming cosmopolitan coccolithophore Emiliania huxleyi and its viruses (EhVs) are a model for density-dependent virulent dynamics. EhVs commonly exhibit rapid viral reproduction and drive host death in high-density laboratory cultures and mesocosms that simulate blooms. Here we show that this system exhibits physiology-dependent temperate dynamics at environmentally relevant E. huxleyi host densities rather than virulent dynamics, with viruses switching from a long-term non-lethal temperate phase in healthy hosts to a lethal lytic stage as host cells become physiologically stressed. Using this system as a model for temperate infection dynamics, we present a template to diagnose temperate infection in other virus–host systems by integrating experimental, theoretical, and environmental approaches. Finding temperate dynamics in such an established virulent host–virus model system indicates that temperateness may be more pervasive than previously considered, and that the role of viruses in bloom formation and decline may be governed by host physiology rather than by host–virus densities

    Systematic voiding programme in adults with urinary incontinence following acute stroke: the ICONS-II RCT

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    Background: Urinary incontinence affects around half of stroke survivors in the acute phase, and it often presents as a new problem after stroke or, if pre-existing, worsens significantly, adding to the disability and helplessness caused by neurological deficits. New management programmes after stroke are needed to address urinary incontinence early and effectively. Objective: The Identifying Continence OptioNs after Stroke (ICONS)-II trial aimed to evaluate the clinical effectiveness and cost-effectiveness of a systematic voiding programme for urinary incontinence after stroke in hospital. Design: This was a pragmatic, multicentre, individual-patient-randomised (1 : 1), parallel-group trial with an internal pilot. Setting: Eighteen NHS stroke services with stroke units took part. Participants: Participants were adult men and women with acute stroke and urinary incontinence, including those with cognitive impairment. Intervention: Participants were randomised to the intervention, a systematic voiding programme, or to usual care. The systematic voiding programme comprised assessment, behavioural interventions (bladder training or prompted voiding) and review. The assessment included evaluation of the need for and possible removal of an indwelling urinary catheter. The intervention began within 24 hours of recruitment and continued until discharge from the stroke unit. Main outcome measures: The primary outcome measure was severity of urinary incontinence (measured using the International Consultation on Incontinence Questionnaire) at 3 months post randomisation. Secondary outcome measures were taken at 3 and 6 months after randomisation and on discharge from the stroke unit. They included severity of urinary incontinence (at discharge and at 6 months), urinary symptoms, number of urinary tract infections, number of days indwelling urinary catheter was in situ, functional independence, quality of life, falls, mortality rate and costs. The trial statistician remained blinded until clinical effectiveness analysis was complete. Results: The planned sample size was 1024 participants, with 512 allocated to each of the intervention and the usual-care groups. The internal pilot did not meet the target for recruitment and was extended to March 2020, with changes made to address low recruitment. The trial was paused in March 2020 because of COVID-19, and was later stopped, at which point 157 participants had been randomised (intervention, n = 79; usual care, n = 78). There were major issues with attrition, with 45% of the primary outcome data missing: 56% of the intervention group data and 35% of the usual-care group data. In terms of the primary outcome, patients allocated to the intervention group had a lower score for severity of urinary incontinence (higher scores indicate greater severity in urinary incontinence) than those allocated to the usual-care group, with means (standard deviations) of 8.1 (7.4) and 9.1 (7.8), respectively. Limitations: The trial was unable to recruit sufficient participants and had very high attrition, which resulted in seriously underpowered results. Conclusions: The internal pilot did not meet its target for recruitment and, despite recruitment subsequently being more promising, it was concluded that the trial was not feasible owing to the combined problems of poor recruitment, poor retention and COVID-19. The intervention group had a slightly lower score for severity of urinary incontinence at 3 months post randomisation, but this result should be interpreted with caution. Future work: Further studies to assess the effectiveness of an intervention starting in or continuing into the community are required

    Peralkaline Felsic Magmatism of the Atlantic Islands

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    The oceanic-island magmatic systems of the Atlantic Ocean exhibit significant diversity in their respective sizes, ages, and the compositional ranges of their eruptive products. Nevertheless, almost all of the Atlantic islands and island groups have produced peralkaline felsic magmas, implying that similar petrogenetic regimes may be operating throughout the Atlantic Ocean, and arguably elsewhere. The origins of peralkaline magmas are frequently linked to low-degree partial melting of enriched mantle, followed by protracted differentiation in the shallow crust. However, additional petrogenetic processes such as magma mixing, crustal melting, and contamination have been identified at numerous peralkaline centers. The onset of peralkalinity leads to magma viscosities lower than those typical for metaluminous felsic magmas, which has profound implications for processes such as crystal settling. This study represents a compilation of published and original data which demonstrates trends that suggest that the peralkaline magmas of the Atlantic Ocean islands are generated primarily via extended (up to ∼ 95%), open system fractional crystallization of mantle-derived mafic magmas. Crustal assimilation is likely to become more significant as the system matures and fusible material accumulates in the crust. Magma mixing may occur between various compositional end-members and may be recognized via hybridized intermediate magmas. The peralkaline magmas are hydrous, and frequently zoned in composition, temperature, and/or water content. They are typically stored in shallow crustal magma reservoirs (∼ 2–5 km), maintained by mafic replenishment. Low melt viscosities (1 × 101.77 to 1 × 104.77 Pa s) facilitate two-phase flow, promoting the formation of alkali-feldspar crystal mush. This mush may then contribute melt to an overlying melt lens via filter pressing or partial melting. We utilize a three-stage model to account for the establishment, development, and termination of peralkaline magmatism in the ocean island magmatic systems of the Atlantic. We suggest that the overall control on peralkaline magmatism in the Atlantic is magma flux rate, which controls the stability of upper crustal magma reservoirs. The abundance of peralkaline magmas in the Atlantic suggests that their development must be a common, but not inevitable, stage in the evolution of ocean islands

    Spatial growth rate of emerging SARS-CoV-2 lineages in England, September 2020-December 2021

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    This paper uses a robust method of spatial epidemiological analysis to assess the spatial growth rate of multiple lineages of SARS-CoV-2 in the local authority areas of England, September 2020–December 2021. Using the genomic surveillance records of the COVID-19 Genomics UK (COG-UK) Consortium, the analysis identifies a substantial (7.6-fold) difference in the average rate of spatial growth of 37 sample lineages, from the slowest (Delta AY.4.3) to the fastest (Omicron BA.1). Spatial growth of the Omicron (B.1.1.529 and BA) variant was found to be 2.81× faster than the Delta (B.1.617.2 and AY) variant and 3.76× faster than the Alpha (B.1.1.7 and Q) variant. In addition to AY.4.2 (a designated variant under investigation, VUI-21OCT-01), three Delta sublineages (AY.43, AY.98 and AY.120) were found to display a statistically faster rate of spatial growth than the parent lineage and would seem to merit further investigation. We suggest that the monitoring of spatial growth rates is a potentially valuable adjunct to outbreak response procedures for emerging SARS-CoV-2 variants in a defined population

    The place of imagination in ELT teacher education

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    In this workshop participants will be invited to engage with metaphors and fictional narratives and to discuss their potential role in ELT teacher education. It will also briefly examine the place of imagination in western thinking, its reflections in ELT teaching models and approaches, and the interplay between imagination, construction of knowledge, reflection and educational change

    Downstream regulation of CO2 emissions in California’s electricity sector.” Energy Policy 64

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    Abstract This paper examines the implications of alternative forms of cap-and-trade regulations on the California electricity market. Specific focus is given to the implementation of a downstream form of regulation known as the first-deliverer policy. Under this policy, importers (i.e., first-deliverers) of electricity into California are responsible for the emissions associated with the power plants from which the power originated, even if those plants are physically located outside of California. We find that, absent strict non-economic barriers to changing import patterns, such policies are extremely vulnerable to reshuffling of import resources

    Combining sensory evaluations and experimental auctions to assess consumers’ preferences for fresh fruit quality characteristics

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    A combination of sensory evaluation and experimental auctions was used to analyze consumer preferences for external and internal quality characteristics of two fresh apple varieties “Honeycrisp” and “Gala.” A group of 384 panelists in three locations in the United States evaluated the appearance, the internal quality characteristics, in three sequential rounds, for the two apple variety samples. Each panelist responded to a sensory evaluation questionnaire, and then bid on the samples in an incentive compatible second price auction. We found that panelists’ bids increased with the amount of information given. Also, we found that for some attributes such as sweetness, panelists preferred levels closer to their ideal rather than objectively measured higher levels. When evaluating consumers’ preference and valuation for different fresh fruit varieties, a greater explanatory power is obtained when including an indicator variable for the variety along with the set of quality attributes. The indicator variable could improve the control of inherent factors related with the varieties but cannot be observed or inferred easily. Finally, our findings add to previous studies in that flavor, when expressed as a combination of sweetness and acidity in addition to textural attributes, are important determinants of consumers’ acceptance. [EconLit citations: Q13
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