850 research outputs found
Risk and Business Goal Based Security Requirement and Countermeasure Prioritization
Companies are under pressure to be in control of their assets but at the same time they must operate as efficiently as possible. This means that they aim to implement “good-enough security” but need to be able to justify their security investment plans. Currently companies achieve this by means of checklist-based security assessments, but these methods are a way to achieve consensus without being able to provide justifications of countermeasures in terms of business goals. But such justifications are needed to operate securely and effectively in networked businesses. In this paper, we first compare a Risk-Based Requirements Prioritization method (RiskREP) with some requirements engineering and risk assessment methods based on their requirements elicitation and prioritization properties. RiskREP extends misuse case-based requirements engineering methods with IT architecture-based risk assessment and countermeasure definition and prioritization. Then, we present how RiskREP prioritizes countermeasures by linking business goals to countermeasure specification. Prioritizing countermeasures based on business goals is especially important to provide the stakeholders with structured arguments for choosing a set of countermeasures to implement. We illustrate RiskREP and how it prioritizes the countermeasures it elicits by an application to an action case
Warm Dark Haloes Accretion Histories and their Gravitational Signatures
We study clusters in Warm Dark Matter (WDM) models of a thermally produced
dark matter particle keV in mass. We show that, despite clusters in WDM
cosmologies having similar density profiles as their Cold Dark Matter (CDM)
counterparts, the internal properties, such as the amount of substructure,
shows marked differences. This result is surprising as clusters are at mass
scales that are {\em a thousand times greater} than that at which structure
formation is suppressed. WDM clusters gain significantly more mass via smooth
accretion and contain fewer substructures than their CDM brethren. The higher
smooth mass accretion results in subhaloes which are physically more extended
and less dense. These fine-scale differences can be probed by strong
gravitational lensing. We find, unexpectedly, that WDM clusters have {\em
higher} lensing efficiencies than those in CDM cosmologies, contrary to the
naive expectation that WDM clusters should be less efficient due to the fewer
substructures they contain. Despite being less dense, the larger WDM subhaloes
are more likely to have larger lensing cross-sections than CDM ones.
Additionally, WDM subhaloes typically reside at larger distances, which
radially stretches the critical lines associated with strong gravitational
lensing, resulting in excess in the number of clusters with large radial
cross-sections at the level. Though lensing profile for an
individual cluster vary significantly with the line-of-sight, the radial arc
distribution based on a sample of clusters may prove to be the
crucial test for the presence of WDM.Comment: 13 pages, 14 figures, submitted to MNRA
Hidden from view: Coupled Dark Sector Physics and Small Scales
We study cluster mass dark matter haloes, their progenitors and surroundings
in an coupled Dark Matter-Dark Energy model and compare it to quintessence and
CDM models with adiabatic zoom simulations. When comparing cosmologies
with different expansions histories, growth functions & power spectra, care
must be taken to identify unambiguous signatures of alternative cosmologies.
Shared cosmological parameters, such as , need not be the same for
optimal fits to observational data. We choose to set our parameters to
CDM values. We find that in coupled models, where DM decays into
DE, haloes appear remarkably similar to CDM haloes despite DM
experiencing an additional frictional force. Density profiles are not
systematically different and the subhalo populations have similar mass, spin,
and spatial distributions, although (sub)haloes are less concentrated on
average in coupled cosmologies. However, given the scatter in related
observables (), this difference is unlikely to
distinguish between coupled and uncoupled DM. Observations of satellites of MW
and M31 indicate a significant subpopulation reside in a plane. Coupled models
do produce planar arrangements of satellites of higher statistical significance
than CDM models, however, in all models these planes are dynamically
unstable. In general, the nonlinear dynamics within and near large haloes masks
the effects of a coupled dark sector. The sole environmental signature we find
is that small haloes residing in the outskirts are more deficient in baryons
than their CDM counterparts. The lack of a pronounced signal for a
coupled dark sector strongly suggests that such a phenomena would be
effectively hidden from view.Comment: 13 pages, 14 figures, 2 tables, accepted for publication in MNRA
Heating of galactic gas by dark matter annihilation in ultracompact minihalos
The existence of substructure in halos of annihilating dark matter would be
expected to substantially boost the rate at which annihilation occurs.
Ultracompact minihalos of dark matter (UCMHs) are one of the more extreme
examples of this. The boosted annihilation can inject significant amounts of
energy into the gas of a galaxy over its lifetime. Here we determine the impact
of the boost factor from UCMH substructure on the heating of galactic gas in a
Milky Way-type galaxy, by means of N-body simulation. If of the dark
matter exists as UCMHs, the corresponding boost factor can be of order .
For reasonable values of the relevant parameters (annihilation cross section
, dark matter mass 100 GeV,
10% heating efficiency), we show that the presence of UCMHs at the 0.1% level
would inject enough energy to eject significant amounts of gas from the halo,
potentially preventing star formation within 1 kpc of the halo centre.Comment: 14 pages, 3 figure
Future and advances in endoscopy
The future of endoscopy will be dictated by rapid technological advances in the development of light sources, optical fibers, and miniature scanners that will allow for images to be collected in multiple spectral regimes, with greater tissue penetration, and in three dimensions. These engineering breakthroughs will be integrated with novel molecular probes that are highly specific for unique proteins to target diseased tissues. Applications include early cancer detection by imaging molecular changes that occur before gross morphological abnormalities, personalized medicine by visualizing molecular targets specific to individual patients, and image guided therapy by localizing tumor margins and monitoring for recurrence. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87084/1/471_ftp.pd
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