1,498 research outputs found

    K-bass: A Knowledge–Based Access Security System For Medical Environments

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    Enforcing security requires the application of an access control model. The access control models used today have limitations that become evident when applied in collaborative environments, such as medical environments. To overcome these problems, a system has been developed in order to introduce dynamic access security. The system at hand combines effectively (C-TMAC) Team-based access control using contexts model and knowledge base technology. The system’s security scheme fine-grains the users’ access rights by integrating the Role Based Access Controls (RBAC) model and the (C-TMAC) model through knowledge-based systems technology. The originality lies on the fact that the users in the system are authenticated by combining their individual access rights (RBAC), their team’s access rights (C-TMAC) and the context information associated with the team they belong to. Furthermore, knowledge-based technology is used for the representation of knowledge and reasoning. The system initiates with some facts and rules and is able to learn, infer knowledge and produce meta-knowledge. Therefore the system can train itself and respond in non-deterministic way to user requests. Any change in context information fires a new rule in the knowledge base. The proposed system is an automated and self-controlled system called (K-BASS) Knowledge-based Access Security System that may be used in medical environments, to dynamically assign permission rights and to add new medical staff and patients

    Exact Gravity Dual of a Gapless Superconductor

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    A model of an exact gravity dual of a gapless superconductor is presented in which the condensate is provided by a charged scalar field coupled to a bulk black hole of hyperbolic horizon in asymptotically AdS spacetime. Below a critical temperature, the black hole acquires its hair through a phase transition while an electromagnetic perturbation of the background Maxwell field determines the conductivity of the boundary theory.Comment: 21 pages, 8 figures, a section on the stability of the MTZ black hole is added, references are added, version to be published in JHE

    Microbial load on smoked fish commonly traded in Ibadan, Oyo State, Nigeria

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    The microbial load on smoked fish sold in Ibadan, Oyo State was studied. 64 of 4 different fish species (Mackerel (Scomber scombrus), Sardine (Sardinela eba), Panla (Gadus morhua) and Cat fish (Clarias gariepinus)) were sourced from five different market locations. The microbiological analysis was done using standard microbiological procedures. The bacterial count of fish sampled from Ojo market was the highest (0.35±0.11 x 103 CFU/g) while the bacteria count of the fish sample from Bodija market was the lowest (0.07±0.04 x 103 CFU/g). There was no significant difference (p>0.05) in the microbial load of the various fish species sold within Ibadan metropolis as well as fish sampled from various market locations in Ibadan metropolis. Bacterial isolated on smoked fish studied were: E. coli, Salmonella spp, Klebsiella spp, Staphylococcus aureus, Aerosomonas spp, Pseudomonas spp, Vibrio spp, Serratia spp, Chromobacterium spp, Enterobacteria spp and Shigella spp. While the following fungi were isolated from the study: Aspergillus flavus, Penicillium spp, Fusarium oxysporum, Trrichoderma spp and Ceotrichium albidium. Fish species sold in different markets within Ibadan metropolis is fit for human consumption. Caution should be exercised in consuming smoked-dried fish displayed openly, reheating may be necessary to activate such micro-organisms before consumption.Keywords: bacteria, fungi, market, fish specie

    Drug-mediated shortening of action potentials in LQTS2 hiPSC-cardiomyocytes

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    Cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSCs) are now a well-established modality for modeling genetic disorders of the heart. This is especially so for long QT syndrome (LQTS), which is caused by perturbation of ion channel function, and can lead to fainting, malignant arrhythmias and sudden cardiac death. LQTS2 is caused by mutations in KCNH2, a gene whose protein product contributes to IKr (also known as HERG), which is the predominant repolarizing potassium current in CMs. β-blockers are the mainstay treatment for patients with LQTS, functioning by reducing heart rate and arrhythmogenesis. However, they are not effective in around a quarter of LQTS2 patients, in part, because they do not correct the defining feature of the condition, which is excessively prolonged QT interval. Since new therapeutics are needed, in this report, we biopsied skin fibroblasts from a patient who was both genetically and clinically diagnosed with LQTS2. By producing LQTS-hiPSC-CMs, we assessed the impact of different drugs on action potential duration (APD), which is used as an in vitro surrogate for QT interval. Not surprisingly, the patient's own β-blocker medication, propranolol, had a marginal effect on APD in the LQTS-hiPSC-CMs. However, APD could be significantly reduced by up to 19% with compounds that enhanced the IKr current by direct channel binding or by indirect mediation through the PPARδ/protein 14-3-3 epsilon/HERG pathway. Drug-induced enhancement of an alternative potassium current, IKATP, also reduced APD by up to 21%. This study demonstrates the utility of LQTS-hiPSC-CMs in evaluating whether drugs can shorten APD and, importantly, shows that PPARδ agonists may form a new class of therapeutics for this condition

    Insights into the transfer of silicon isotopes into the sediment record

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    The first δ30Sidiatom data from lacustrine sediment traps are presented from Lake Baikal, Siberia. Data are compared with March surface water (upper 180 m) δ30SiDSi compositions for which a mean value of +2.28‰ ±  0.09 (95 % confidence) is derived. This value acts as the pre-diatom bloom baseline silicic acid isotopic composition of waters (δ30SiDSi initial). Open traps were deployed along the depth of the Lake Baikal south basin water column between 2012 and 2013. Diatom assemblages display a dominance ( > 85 %) of the spring/summer bloom species Synedra acus var radians, so that δ30Sidiatom compositions reflect predominantly spring/summer bloom utilisation. Diatoms were isolated from open traps and, in addition, from 3-monthly (sequencing) traps (May, July and August 2012) for δ30Sidiatom analyses. Mean δ30Sidiatom values for open traps are +1.23‰ ±  0.06 (at 95 % confidence and MSWD of 2.9, n = 10). Total dry mass sediment fluxes are highest in June 2012, which we attribute to the initial export of the dominant spring diatom bloom. We therefore argue that May δ30Sidiatom signatures (+0.67‰ ±  0.06, 2σ) when compared with mean upper water δ30SiDSi initial (e.g. pre-bloom) signatures can be used to provide a snapshot estimation of diatom uptake fractionation factors (ϵuptake) in Lake Baikal. A ϵuptake estimation of −1.61 ‰ is therefore derived, although we emphasise that synchronous monthly δ30SiDSi and δ30Sidiatom data would be needed to provide more robust estimations and therefore more rigorously test this, particularly when taking into consideration any progressive enrichment of the DSi pool as blooms persist. The near-constant δ30Sidiatom composition in open traps demonstrates the full preservation of the signal through the water column and thereby justifies the use and application of the technique in biogeochemical and palaeoenvironmental research. Data are finally compared with lake sediment core samples, collected from the south basin. Values of +1.30‰ ±  0.08 (2σ) and +1.43‰ ±  0.13 (2σ) were derived for cores BAIK13-1C (0.6–0.8 cm core depth) and at BAIK13-4F (0.2–0.4 cm core depth) respectively. Trap data highlight the absence of a fractionation factor associated with diatom dissolution (ϵdissolution) (particularly as Synedra acus var radians, the dominant taxa in the traps, is very susceptible to dissolution) down the water column and in the lake surface sediments, thus validating the application of δ30Sidiatom analyses in Lake Baikal and other freshwater systems, in palaeoreconstructions

    Fermions on spontaneously generated spherical extra dimensions

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    We include fermions to the model proposed in hep-th/0606021, and obtain a renormalizable 4-dimensional SU(N) gauge theory which spontaneously generates fuzzy extra dimensions and behaves like Yang-Mills theory on M^4 \times S^2. We find a truncated tower of fermionic Kaluza-Klein states transforming under the low-energy gauge group, which is found to be either SU(n), or SU(n_1) x SU(n_2) x U(1). The latter case implies a nontrivial U(1) flux on S^2, leading to would-be zero modes for the bifundamental fermions. In the non-chiral case they may pair up to acquire a mass, and the emerging picture is that of mirror fermions. We discuss the possible implementation of a chirality constraint in 6 dimensions, which is nontrivial at the quantum level due to the fuzzy nature of the extra dimensions.Comment: 34 pages. V2: references added, minor corrections V3: discussion added, final versio

    Causality and the speed of sound

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    A usual causal requirement on a viable theory of matter is that the speed of sound be at most the speed of light. In view of various recent papers querying this limit, the question is revisited here. We point to various issues confronting theories that violate the usual constraint.Comment: v2: additional discussion on models that appear to have superluminal signal speeds; version to appear in GR

    Dynamical generation of fuzzy extra dimensions, dimensional reduction and symmetry breaking

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    We present a renormalizable 4-dimensional SU(N) gauge theory with a suitable multiplet of scalar fields, which dynamically develops extra dimensions in the form of a fuzzy sphere S^2. We explicitly find the tower of massive Kaluza-Klein modes consistent with an interpretation as gauge theory on M^4 x S^2, the scalars being interpreted as gauge fields on S^2. The gauge group is broken dynamically, and the low-energy content of the model is determined. Depending on the parameters of the model the low-energy gauge group can be SU(n), or broken further to SU(n_1) x SU(n_2) x U(1), with mass scale determined by the size of the extra dimension.Comment: 27 pages. V2: discussion and references added, published versio

    A New Class of Exact Hairy Black Hole Solutions

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    We present a new class of black hole solutions with minimally coupled scalar field in the presence of a negative cosmological constant. We consider a one-parameter family of self-interaction potentials parametrized by a dimensionless parameter gg. When g=0g=0, we recover the conformally invariant solution of the Martinez-Troncoso-Zanelli (MTZ) black hole. A non-vanishing gg signals the departure from conformal invariance. All solutions are perturbatively stable for negative black hole mass and they may develop instabilities for positive mass. Thermodynamically, there is a critical temperature at vanishing black hole mass, where a higher-order phase transition occurs, as in the case of the MTZ black hole. Additionally, we obtain a branch of hairy solutions which undergo a first-order phase transition at a second critical temperature which depends on gg and it is higher than the MTZ critical temperature. As g0g\to 0, this second critical temperature diverges.Comment: 18 pages, 6 figures, minor changes, references added, published versio
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