3,616 research outputs found
Residual generic ergodicity of periodic group extensions over translation surfaces
Continuing the work in \cite{ergodic-infinite}, we show that within each
stratum of translation surfaces, there is a residual set of surfaces for which
the geodesic flow in almost every direction is ergodic for almost-every
periodic group extension produced using a technique referred to as \emph{cuts}
Polarization enhancement in two- and three-component ferroelectric superlattices
Composition-dependent structural and polar properties of epitaxial
short-period CaTiO_3/SrTiO_3/BaTiO_3 superlattices grown on a SrTiO_3 substrate
are investigated with first-principles density-functional theory computational
techniques. Polarization enhancement with respect to bulk tetragonal BaTiO_3 is
found for two- and three-component superlattices with a BaTiO_3 concentration
of more than 30%. Individual BaTiO_3 layer thickness is identified as an
important factor governing the polarization improvement. In addition, the
degree of inversion-symmetry breaking in three-component superlattices can be
controlled by varying the thicknesses of the component layers. The flexibility
allowed within this large family of structures makes them highly suitable for
various applications in modern nano-electro-mechanical devices.Comment: The following article has been submitted to Applied Physics Letters.
After it is published, it will be found at http://apl.aip.org
Android Permissions Remystified: A Field Study on Contextual Integrity
Due to the amount of data that smartphone applications can potentially
access, platforms enforce permission systems that allow users to regulate how
applications access protected resources. If users are asked to make security
decisions too frequently and in benign situations, they may become habituated
and approve all future requests without regard for the consequences. If they
are asked to make too few security decisions, they may become concerned that
the platform is revealing too much sensitive information. To explore this
tradeoff, we instrumented the Android platform to collect data regarding how
often and under what circumstances smartphone applications are accessing
protected resources regulated by permissions. We performed a 36-person field
study to explore the notion of "contextual integrity," that is, how often are
applications accessing protected resources when users are not expecting it?
Based on our collection of 27 million data points and exit interviews with
participants, we examine the situations in which users would like the ability
to deny applications access to protected resources. We found out that at least
80% of our participants would have preferred to prevent at least one permission
request, and overall, they thought that over a third of requests were invasive
and desired a mechanism to block them
Estrogen Receptor Transrepresses Brain Inflammation
Estrogen receptors (ERs) have long been implicated in the etiology of multiple sclerosis, but no clear molecular mechanisms have linked ERs to the disease's pathology. Now Saijo et al. (2011) provide evidence that ERβ activates a transrepression pathway that suppresses inflammation and inhibits progression of pathology in a mouse model of multiple sclerosis
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