1,409 research outputs found

    Half-BPS quotients in M-theory: ADE with a twist

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    We classify Freund-Rubin backgrounds of eleven-dimensional supergravity of the form AdS_4 x X^7 which are at least half BPS; equivalently, smooth quotients of the round 7-sphere by finite subgroups of SO(8) which admit an (N>3)-dimensional subspace of Killing spinors. The classification is given in terms of pairs consisting of an ADE subgroup of SU(2) and an automorphism defining its embedding in SO(8). In particular we find novel half-BPS quotients associated with the subgroups of type D_n (for n>5), E_7 and E_8 and their outer automorphisms.Comment: 16 pages; V2: notational inconsistencies addressed, final version to be published in JHE

    The Triads Geometric Consistency Index in AHP-Pairwise Comparison Matrices

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    The paper presents the Triads Geometric Consistency Index (T-GCI), a measure for evaluating the inconsistency of the pairwise comparison matrices employed in the Analytic Hierarchy Process (AHP). Based on the Saaty''s definition of consistency for AHP, the new measure works directly with triads of the initial judgements, without having to previously calculate the priority vector, and therefore is valid for any prioritisation procedure used in AHP. The T-GCI is an intuitive indicator defined as the average of the log quadratic deviations from the unit of the intensities of all the cycles of length three. Its value coincides with that of the Geometric Consistency Index (GCI) and this allows the utilisation of the inconsistency thresholds as well as the properties of the GCI when using the T-GCI. In addition, the decision tools developed for the GCI can be used when working with triads (T-GCI), especially the procedure for improving the inconsistency and the consistency stability intervals of the judgements used in group decision making. The paper further includes a study of the computational complexity of both measures (T-GCI and GCI) which allows selecting the most appropriate expression, depending on the size of the matrix. Finally, it is proved that the generalisation of the proposed measure to cycles of any length coincides with the T-GCI. It is not therefore necessary to consider cycles of length greater than three, as they are more complex to obtain and the calculation of their associated measure is more difficult

    AHP-group decision making based on consistency

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    The Precise consistency consensus matrix (PCCM) is a consensus matrix for AHP-group decision making in which the value of each entry belongs, simultaneously, to all the individual consistency stability intervals. This new consensus matrix has shown significantly better behaviour with regards to consistency than other group consensus matrices, but it is slightly worse in terms of compatibility, understood as the discrepancy between the individual positions and the collective position that synthesises them. This paper includes an iterative algorithm for improving the compatibility of the PCCM. The sequence followed to modify the judgments of the PCCM is given by the entries that most contribute to the overall compatibility of the group. The procedure is illustrated by means of its application to a real-life situation (a local context) with three decision makers and four alternatives. The paper also offers, for the first time in the scientific literature, a detailed explanation of the process followed to solve the optimisation problem proposed for the consideration of different weights for the decision makers in the calculation of the PCCM

    Designed to fail : a biopolitics of British Citizenship.

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    Tracing a route through the recent 'ugly history' of British citizenship, this article advances two central claims. Firstly, British citizenship has been designed to fail specific groups and populations. Failure, it argues, is a design principle of British citizenship, in the most active and violent sense of the verb to design: to mark out, to indicate, to designate. Secondly, British citizenship is a biopolitics - a field of techniques and practices (legal, social, moral) through which populations are controlled and fashioned. This article begins with the 1981 Nationality Act and the violent conflicts between the police and black communities in Brixton that accompanied the passage of the Act through the British parliament. Employing Michel Foucault's concept of state racism, it argues that the 1981 Nationality Act marked a pivotal moment in the design of British citizenship and has operated as the template for a glut of subsequent nationality legislation that has shaped who can achieve citizenship. The central argument is that the existence of populations of failed citizens within Britain is not an accident of flawed design, but is foundational to British citizenship. For many 'national minorities' the lived realities of biopolitical citizenship stand in stark contradistinction to contemporary governmental accounts of citizenship that stress community cohesion, political participation, social responsibility, rights and pride in shared national belonging

    Capacitively Coupled Electrical Stimulation of Rat Chondroepiphysis Explants: A Histomorphometric Analysis

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    [EN] The growth plate is a cartilaginous layer present from the gestation period until the end of puberty where it ossifies joining diaphysis and epiphysis. During this period several endocrine, autocrine, and paracrine processes within the growth plate are carried out by chondrocytes; therefore, a disruption in cellular functions may lead to pathologies affecting bone development. It is known that electric fields impact the growth plate; however, parameters such as stimulation time and electric field intensity are not well documented. Accordingly, this study presents a histomorphometrical framework to assess the effect of electric fields on chondroepiphysis ex-plants. Bones were stimulated with 3.5 and 7 mV/cm, and for each electric field two exposure times were tested for 30 days (30 min and 1 h). Results evidenced that electric fields increased the hypertrophic zones compared with controls. In addition, a stimulation of 3.5 mV/cm applied for 1 h preserved the columnar cell density and its orientation. Moreover, a pre-hypertrophy differentiation in the center of the chondroepiphysis was observed when explants were stimulated during 1 h with both electric fields. These findings allow the understanding of the effect of electrical stimulation over growth plate organization and how the stimulation modifies chondrocytes morphophysiology.This research was supported by COLCIENCIAS Administrative Department of Science, Technology and Innovation. The authors gratefully thank the research support from the Biotechnology Institute of the Universidad Nacional de Colombia, for providing the lab space at the Biomimetics Laboratory and the reactants to perform the experimental approach of this study. Research reported in this publication was supported by COLCIENCIAS Administrative Department of Science, Technology and Innovation (Announcement 712-2015 Grant No 50457).Vaca-González, JJ.; Escobar, J.; Guevara, J.; Hata, YA.; Gallego Ferrer, G.; Garzón-Alvarado, DA. (2019). Capacitively Coupled Electrical Stimulation of Rat Chondroepiphysis Explants: A Histomorphometric Analysis. Bioelectrochemistry. 126:1-11. https://doi.org/10.1016/j.bioelechem.2018.11.004S11112

    On a spin conformal invariant on manifolds with boundary

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    On a n-dimensional connected compact manifold with non-empty boundary equipped with a Riemannian metric, a spin structure and a chirality operator, we study some properties of a spin conformal invariant defined from the first eigenvalue of the Dirac operator under the chiral bag boundary condition. More precisely, we show that we can derive a spinorial analogue of Aubin's inequality.Comment: 26 page

    Assessing Value-based Health Care Delivery for Hemodialysis

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    Rationale, aims and objectives Disparities in haemodialysis outcomes among centres have been well-documented. Besides, attempts to assess haemodialysis results have been based on non-comprehensive methodologies. This study aimed to develop a comprehensive methodology for assessing haemodialysis centres, based on the value of health care. The value of health care is defined as the patient benefit from a specific medical intervention per monetary unit invested (Value = Patient Benefit/Cost). This study assessed the value of health care and ranked different haemodialysis centres. Method A nephrology quality management group identified the criteria for the assess- ment. An expert group composed of stakeholders (patients, clinicians and managers) agreed on the weighting of each variable, considering values and preferences. Multi-criteria methodology was used to analyse the data. Four criteria and their weights were identified: evidence-based clinical performance measures = 43 points; yearly mortality = 27 points; patient satisfaction = 13 points; and health-related quality of life = 17 points (100-point scale). Evidence-based clinical performance measures included five sub-criteria, with respective weights, including: dialysis adequacy; haemoglobin concentration; mineral and bone disorders; type of vascular access; and hospitalization rate. The patient benefit was determined from co-morbidity–adjusted results and corresponding weights. The cost of each centre was calculated as the average amount expended per patient per year. Results The study was conducted in five centres (1–5). After adjusting for co-morbidity, value of health care was calculated, and the centres were ranked. A multi-way sensitivity analysis that considered different weights (10–60% changes) and costs (changes of 10% in direct and 30% in allocated costs) showed that the methodology was robust. The rankings: 4-5-3-2-1 and 4-3-5-2-1 were observed in 62.21% and 21.55%, respectively, of simula- tions, when weights were varied by 60%. Conclusions Value assessments may integrate divergent stakeholder perceptions, create a context for improvement and aid in policy-making decisions

    Information impact on consumers' perceptions towards aquaculture : Dismantling the myth about feeds for farmed fish

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    Altres ajuts: Acord transformatiu CRUE-CSICAquaculture products are commonplace in markets around the world. However, despite efforts to minimize the negative perceptions towards aquaculture, several misbeliefs or myths still persist, and thus globally consumers tend to value wild fish more highly than farmed fish. The lack of information has been shown to be one of the most important causes of this preference, driving buying decisions to be more emotional than rational. The aim of this study was to determine whether scientific-supported information contrasting one myth could contribute to a better perception of farmed products. To that end, consensus on a series of aquaculture-related issues among different scientists, external experts, and aquaculture societies was used to build up the scientific information. This information was provided to 300 Spanish consumers using two different communication tools (150 consumers each tool): an interactive web documentary and a written and printed document, to detect possible differences in the change of consumers' perception. Consumers were asked for their degree of agreement on a set of 14 statements before and after providing the scientific information. A variable collecting the assessment of each of the statements was calculated as the Overall-perception. Possible significant differences between the scores before and after providing the information and for the 'overall perception' were analysed separately for each communication tool as well as for the combined sample. Possible relationship between the consumers' perception with the sociodemographic factors, the consumers' knowledge and the fish consumption habits were also assessed. Results show that consumer's perception of aquaculture before the query were moderate (5.6 average in a 0 to 10 scale) but that it increased slightly but significantly and regardless of the communication tool used. Among sociodemographic factors, age and gender were the ones that most influenced consumer's perceptions, being older people those who exhibited a generally more positive opinion towards aquaculture. The effects of consumption habits and knowledge about aquaculture were also the two most explicative factors for change in perception. Importantly, the opinion of consumers with less knowledge about seafood products in general and production methods or consuming only wild fish products, improved after being exposed to the information. These results demonstrate the utility of science- and fact-based communication campaigns to improve the societal perception of aquaculture practices and products, regardless of the tool used to transmit this information
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