748 research outputs found
Service Security and Privacy as a Socio-Technical Problem: Literature review, analysis methodology and challenge domains
Published online September 2015 accepted: 15 September 2014Published online September 2015 accepted: 15 September 2014The security and privacy of the data that users transmit, more or less deliberately, to modern services is an open problem. It is not solely limited to the actual Internet traversal, a sub-problem vastly tackled by consolidated research in security protocol design and analysis. By contrast, it entails much broader dimensions pertaining to how users approach technology and understand the risks for the data they enter. For example, users may express cautious or distracted personas depending on the service and the point in time; further, pre-established paths of practice may lead them to neglect the intrusive privacy policy offered by a service, or the outdated protections adopted by another. The approach that sees the service security and privacy problem as a socio-technical one needs consolidation. With this motivation, the article makes a threefold contribution. It reviews the existing literature on service security and privacy, especially from the socio-technical standpoint. Further, it outlines a general research methodology aimed at layering the problem appropriately, at suggesting how to position existing findings, and ultimately at indicating where a transdisciplinary task force may fit in. The article concludes with the description of the three challenge domains of services whose security and privacy we deem open socio-technical problems, not only due to their inherent facets but also to their huge number of users
A Discrete Four Stroke Quantum Heat Engine Exploring the Origin of Friction
The optimal power performance of a first principle quantum heat engine model
shows friction-like phenomena when the internal fluid Hamiltonian does not
commute with the external control field. The model is based on interacting
two-level-systems where the external magnetic field serves as a control
variable.Comment: 4 pages 3 figure
Measuring multipole moments of Weyl metrics by means of gyroscopes
Using the technique of Rindler and Perlick we calculate the total precession
per revolution of a gyroscope circumventing the source of Weyl metrics. We
establish thereby a link between the multipole moments of the source and an
``observable'' quantity. Special attention deserves the case of the
gamma-metric. As an extension of this result we also present the corresponding
expressions for some stationary space-times.Comment: 18 pages Latex, To appear in J.Math.Phy
Exact relativistic models of thin disks around static black holes in a magnetic field
The exact superposition of a central static black hole with surrounding thin
disk in presence of a magnetic field is investigated. We consider two models of
disk, one of infinite extension based on a Kuzmin-Chazy-Curzon metric and other
finite based on the first Morgan-Morgan disk. We also analyze a simple model of
active galactic nuclei consisting of black hole, a Kuzmin-Chazy-Curzon disk and
two rods representing jets, in presence of magnetic field. To explain the
stability of the disks we consider the matter of the disk made of two
pressureless streams of counterrotating charged particles (counterrotating
model) moving along electrogeodesic. Using the Rayleigh criterion we derivate
for circular orbits the stability conditions of the particles of the streams.
The influence of the magnetic field on the matter properties of the disk and on
its stability are also analyzed.Comment: 17 pages, 14 figures. arXiv admin note: text overlap with
arXiv:gr-qc/0409109 by other author
Comment on "Superconducting gap anisotropy vs. doping level in high-T_c cuprates" by C. Kendziora et al, PRL 77, 727 (1996)
In a recent paper Kendziora et al concluded that the superconducting gap in
overdoped Bi-2212 is isotropic. From data obtained from electronic Raman
scattering measurements, their conclusion was based on the observation that
pair breaking peaks occured at approximately the same frequency in different
scattering geometries and that the normalized scattering intensity at low
energies was strongly depleted. We discuss a different interpretation of the
raw data and present new data which is consistent with a strongly anisotropic
gap with nodes. The spectra can be successfully described by a model for Raman
scattering in a d_{x^{2}-y^{2}} superconductor with spin fluctuations and
impurity scattering included.Comment: 1 page revtex plus 1 postscript figur
A source of a quasi--spherical space--time: The case for the M--Q solution
We present a physically reasonable source for an static, axially--symmetric
solution to the Einstein equations. Arguments are provided, supporting our
belief that the exterior space--time produced by such source, describing a
quadrupole correction to the Schwarzschild metric, is particularly suitable
(among known solutions of the Weyl family) for discussing the properties of
quasi--spherical gravitational fields.Comment: 34 pages, 9 figures. To appear in GR
Synchronisation in the prefrontal-striatal circuit tracks behavioural choice in a go no-go task in rats
Rodent striatum is involved in sensory-motor transformations and reward-related learning. Lesion studies suggest dorsolateral striatum, dorsomedial striatum, and nucleus accumbens underlie stimulus-response transformations, goal-directed behaviour and reward expectation respectively. In addition, prefrontal inputs likely control these functions. Here we set out to study how reward-driven behaviour is mediated by the coordinated activity of these structures in the intact brain. We implemented a discrimination task requiring rats to either respond or suppress responding on a lever after the presentation of auditory cues in order to obtain rewards. Single unit activity in the striatal subregions and prelimbic cortex was recorded using tetrode arrays. Striatal units showed strong onset responses to auditory cues paired with an opportunity to obtain reward. Cue onset responses in both striatum and cortex were significantly modulated by previous errors suggesting a role of these structures in maintaining appropriate motivation or action selection during ongoing behaviour. Furthermore, failure to respond to the reward-paired tones was associated with higher pre-trial coherence among striatal subregions and between cortex and striatum suggesting a task-negative corticostriatal network whose activity may be suppressed to enable processing of reward-predictive cues. Our findings highlight that coordinated activity in a distributed network including both prelimbic cortex and multiple striatal regions underlies reward-related decisions
The Long-Term Performance of Small-Cell Batteries Without Cell-Balancing Electronics
Tests approx.8 yrs ago showed Sony HC do not imbalance. AEA developed a theory (ESPC 2002): a) Self-discharge (SD) decreases with state-of-charge (SOC); b) Cells diverge to a state of dynamic equilibrium; c) Equilibrium spread depends on cell SD uniformity. Balancing model verified against test data. Short-term measures of SD difficult in Sony cells and very small values, depends on technique. Long-term evidence supports lower SD at low SD. Battery testing best proof of performance, typically mission specific tests
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