651 research outputs found
Network layer access control for context-aware IPv6 applications
As part of the Lancaster GUIDE II project, we have developed a novel wireless access point protocol designed to support the development of next generation mobile context-aware applications in our local environs. Once deployed, this architecture will allow ordinary citizens secure, accountable and convenient access to a set of tailored applications including location, multimedia and context based services, and the public Internet. Our architecture utilises packet marking and network level packet filtering techniques within a modified Mobile IPv6 protocol stack to perform access control over a range of wireless network technologies. In this paper, we describe the rationale for, and components of, our architecture and contrast our approach with other state-of-the- art systems. The paper also contains details of our current implementation work, including preliminary performance measurements
Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy
Spin-polarized low-energy electron microscopy was used to image a magnetite
crystal with (100) surface orientation. Sets of spin-dependent images of
magnetic domain patterns observed in this surface were used to map the
direction of the magnetization vector with high spatial and angular resolution.
We find that domains are magnetized along the surface [110] directions, and
domain wall structures include 90{\deg} and 180{\deg} walls. A type of
unusually curved domain walls are interpreted as N\'eel-capped surface
terminations of 180{\deg} Bloch walls.Comment: 17 pages, 4 figures. Presented at the LEEM-PEEM 8 conferenc
Experimental implementation of a four-player quantum game
Game theory is central to the understanding of competitive interactions
arising in many fields, from the social and physical sciences to economics.
Recently, as the definition of information is generalized to include entangled
quantum systems, quantum game theory has emerged as a framework for
understanding the competitive flow of quantum information. Up till now only
two-player quantum games have been demonstrated. Here we report the first
experiment that implements a four-player quantum Minority game over tunable
four-partite entangled states encoded in the polarization of single photons.
Experimental application of appropriate quantum player strategies give
equilibrium payoff values well above those achievable in the classical game.
These results are in excellent quantitative agreement with our theoretical
analysis of the symmetric Pareto optimal strategies. Our result demonstrate for
the first time how non-trivial equilibria can arise in a competitive situation
involving quantum agents and pave the way for a range of quantum transaction
applications.Comment: 9 pages, 5 figure
Mathematics Underlying the F-Theory/Heterotic String Duality in Eight Dimensions
One of the dualities in string theory, the F-theory/heterotic string duality
in eight dimensions, predicts an interesting correspondence between two
seemingly disparate geometrical objects. On one side of the duality there are
elliptically fibered K3 surfaces with section. On the other side, one finds
elliptic curves endowed with certain flat connections and complexified Kahler
classes. This paper is part of a project aimed at establishing the rigorous
mathematical results describing the geometry underlying the classical aspects
of this duality. The task involves understanding and comparing the classical
moduli spaces on the two sides.Comment: 43 pages, LaTe
Incentivizing Stable Path Selection in Future Internet Architectures
By delegating path control to end-hosts, future Internet architectures offer
flexibility for path selection. However, there is a concern that the
distributed routing decisions by end-hosts, in particular load-adaptive
routing, can lead to oscillations if path selection is performed without
coordination or accurate load information. Prior research has addressed this
problem by devising path-selection policies that lead to stability. However,
little is known about the viability of these policies in the Internet context,
where selfish end-hosts can deviate from a prescribed policy if such a
deviation is beneficial fromtheir individual perspective. In order to achieve
network stability in future Internet architectures, it is essential that
end-hosts have an incentive to adopt a stability-oriented path-selection
policy. In this work, we perform the first incentive analysis of the
stability-inducing path-selection policies proposed in the literature. Building
on a game-theoretic model of end-host path selection, we show that these
policies are in fact incompatible with the self-interest of end-hosts, as these
strategies make it worthwhile to pursue an oscillatory path-selection strategy.
Therefore, stability in networks with selfish end-hosts must be enforced by
incentive-compatible mechanisms. We present two such mechanisms and formally
prove their incentive compatibility.Comment: 38th International Symposium on Computer Performance, Modeling,
Measurements and Evaluation (PERFORMANCE 2020
Erosive effect of different dietary substances on deciduous and permanent teeth.
OBJECTIVES
We investigated the effect of different dietary substances on deciduous and permanent enamel.
MATERIALS AND METHODS
Enamel specimens were prepared from human teeth (n = 108 deciduous molars and n = 108 permanent premolars). We measured the chemical parameters (pH, titratable acidity, viscosity, calcium, phosphate, fluoride concentration and degree of saturation) of nine dietary substances. The teeth were immersed in the respective substance (2 × 2 min; 30 °C; shaking), and we measured the baseline surface hardness (SH) in Vickers hardness numbers (VHN), and the changes in SH after 2 min (ΔSH2-0) and the 4 min (ΔSH4-0) immersion. We analysed the differences between deciduous and permanent teeth using the Wilcoxon test and correlated ΔSH to the different chemical parameters.
RESULTS
Deciduous teeth were significantly softer (549.53 ± 59.41 VHN) than permanent teeth (590.15 ± 55.31 VHN; p < 0.001) at baseline, but they were not more vulnerable to erosive demineralization. Only orange juice, which presented milder erosive potential, caused significantly more demineralisation in deciduous teeth at ΔSH4-0. Practically all chemical parameters significantly correlated with ΔSH (p < 0.05). Substances with lower pH, higher titratable acidity, lower Ca, higher Pi and lower F concentrations, higher viscosity and more undersaturated solutions presented more erosive demineralisation.
CONCLUSION
Different parameters in dietary substances affect erosive demineralisation in deciduous and permanent teeth, but we generally observed no differences in susceptibility to erosion between both types of teeth; only orange juice (less severe acid conditions) caused perceptible differences.
CLINICAL RELEVANCE
We observe that permanent teeth are harder than deciduous teeth, but most substances cause no perceptible difference in erosive demineralisation in both types of teeth
Cross-reactivity among iodinated contrast agents: should we be concerned?
Background
Although several papers deal with "cross-reactivity" in patients with iodinated contrast medium (ICM) hypersensitivity reactions (HSRs), there is no in-depth knowledge of this phenomenon. To define ICM-groups as potential reaction partners and to identify any potential clinical relevance in patients with ICM-HSRs.
Methods
The literature database PubMed was searched for eligible papers dealing with ICM-allergy and "cross-reactivity". The data presented by the papers was analyzed and individual patient data was extracted for re-evaluation based on a definition for both 'polyvalent reactivity' and 'cross-reactivity' as well as for chemical structure-dependent ICM-groups.
Results
Twenty-five original papers (with n=340 extracted patients) formed the study population. Incidences of polyvalent reactivity were non-significantly higher than incidences of cross-reactivity (both range from 0% to 100%). Crossover evaluation in reaction pairings (culprit ICM A with ICM B versus culprit ICM B with ICM A) showed concordance of only 30%. Data support rather non-cross-reactivity (individual reaction pattern) than cross-reactivity constellations.
Conclusions
The obtained results favour an individual reaction pattern, rather than a reactivity driven by chemical structures and so-called cross-reactivity
Hydrogen-induced reversible spin-reorientation transition and magnetic stripe domain phase in bilayer Co on Ru(0001)
Imaging the change in the magnetization vector in real time by spin-polarized
low-energy electron microscopy, we observed a hydrogen-induced, reversible
spin-reorientation transition in a cobalt bilayer on Ru(0001). Initially,
hydrogen sorption reduces the size of out-of-plane magnetic domains and leads
to the formation of a magnetic stripe domain pattern, which can be understood
as a consequence of reducing the out-of-plane magnetic anisotropy. Further
hydrogen sorption induces a transition to an in-plane easy-axis. Desorbing the
hydrogen by heating the film to 400 K recovers the original out-of-plane
magnetization. By means of ab-initio calculations we determine that the origin
of the transition is the local effect of the hybridization of the hydrogen
orbital and the orbitals of the Co atoms bonded to the absorbed hydrogen.Comment: 5 figure
Field Validation of a Non-carcinogenic and Eco-Friendly Disinfectant in a Stand-In Footbath for Treatment of Footrot Associated With aprV2-Positive Strains of Dichelobacter nodosus in Swiss Sheep Flocks.
A national control program for virulent footrot is currently planned in Switzerland. Since commonly used disinfectants either contain heavy metals or are carcinogenic, the aim of this study was to verify the effectiveness of an eco-friendly and non-carcinogenic candidate disinfectant against aprV2-positive strains of Dichelobacter nodosus. Additionally, the effect of the selective use of long-acting oxytetracyclines was evaluated. A total of 18 farms with confirmed footrot infection, randomly allocated to two treatment groups: (1) with antibiotics (AB; n = 9) and, (2) no antibiotics (NAB; n = 9), were included. Claws were carefully trimmed and scored using a scale from 0 (clinically healthy) to 5 (complete loss of the horn capsule) and a prewash waterbath was implemented on 11 farms. Twice-weekly, repeated whole-flock stand-in footbaths with the candidate disinfectant (6%) were performed. Additionally, animals of group AB with a score ≥ 3 were administered oxytetracyclines by injection. On all farms, 10 days after last treatment, aprV2-positive strains could not be detected by risk-based sampling for real-time PCR analysis after 7-21 (median = 12) footbaths with a minimal culling rate of non-responders on nine farms. Farms without contact to other sheep remained without clinical signs of footrot for a minimum of 245 days (mean ± standard deviation: 293.6 ± 23.6). Antibiotic treatment did not reduce the number of footbaths needed. In contrast, a mean of 3.3 disinfecting footbaths could be saved by implementing a prewash waterbath. At animal level, individual and selective use of oxytetracyclines lead to a higher chance (odds ratio = 9.95; 95% CI: 3.54-27.95; p < 0.001) for a lesion score ≥ 3 to improve to a lesion score < 3 within 2 weeks compared to treatment without antibiotics. The test disinfectant is an effective and eco-friendly alternative for the planned Swiss footrot control program and selective use of oxytetracycline has a beneficial impact on the recovery of animals with lesion scores ≥ 3
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