1,523 research outputs found
Checking Interaction-Based Declassification Policies for Android Using Symbolic Execution
Mobile apps can access a wide variety of secure information, such as contacts
and location. However, current mobile platforms include only coarse access
control mechanisms to protect such data. In this paper, we introduce
interaction-based declassification policies, in which the user's interactions
with the app constrain the release of sensitive information. Our policies are
defined extensionally, so as to be independent of the app's implementation,
based on sequences of security-relevant events that occur in app runs. Policies
use LTL formulae to precisely specify which secret inputs, read at which times,
may be released. We formalize a semantic security condition, interaction-based
noninterference, to define our policies precisely. Finally, we describe a
prototype tool that uses symbolic execution to check interaction-based
declassification policies for Android, and we show that it enforces policies
correctly on a set of apps.Comment: This research was supported in part by NSF grants CNS-1064997 and
1421373, AFOSR grants FA9550-12-1-0334 and FA9550-14-1-0334, a partnership
between UMIACS and the Laboratory for Telecommunication Sciences, and the
National Security Agenc
Constraints on Lema\^{\i}tre-Tolman-Bondi models from Observational Hubble Parameter data
We use the observational Hubble parameter data (OHD), both the latest
observational dataset (Stern et al. 2010, referred to as SJVKS) and the
simulated datasets, to constrain Lema\^{\i}tre-Tolman-Bondi (LTB) void models.
The necessity of the consistency check on OHD itself in the LTB cosmology is
stressed. Three voids are chosen as test models and are constrained using the
Union2 dataset of SN Ia as well as OHD. Despite their different
parametrization, the results from our test models show some indicating
similarities, e.g., the best-fit voids obtained from OHD are all considerably
broader than those from SN Ia. Due to the small size of the SJVKS dataset, the
constraints are not conclusive. The constraining power of the future OHD
observations are therefore investigated, through a Figure of Merit (FoM)
analysis based on the Monte Carlo simulated data. We found that, in the case
that the future OHD become more consistent with SN Ia, the results from the
test models are almost unanimous: 1) as many as 32 OHD data points at the
SJVKS-like uncertainty level are needed to give a higher FoM than the Union2
dataset of SN Ia; 2) precise observation helps reduce this required number; 3)
increasing the survey depth does not always increase the FoM. On the other
hand, if the future OHD and the Union2 dataset keep favor different voids, in a
similar manner as they do at present, the 1{\sigma} confidence regions obtained
from the two probes should finally separate. We test this conjecture and found
that, the minimum observational requirement (the size of the dataset, the
uncertainty level and the survey depth) for this inconsistency to emerge
depends strongly on the void model.Comment: 14 pages, 14 figures, 5 tables, accepted for publication in Ap
Towards the design of resilient waste-to-energy systems using Bayesian networks
The concept of resilience has emerged from various domains to address how systems, people and organizations can handle uncertainty. This paper presents a method to improve the resilience of an engineering system by maximizing the system economic lifecycle value, as measured by Net Present Value, under uncertainty. The method is applied to a Waste-to-Energy system based in Singapore and the impact of combining robust and flexible design strategies to improve resilience are discussed. Robust strategies involve optimizing the initial capacity of the system while Bayesian Networks are implemented to choose the flexible expansion strategy that should be deployed given the current observations of demand uncertainties. The Bayesian Network shows promise and should be considered further where decisions are more complex. Resilience is further assessed by varying the volatility of the stochastic demand in the simulation. Increasing volatility generally made the system perform worse since not all demand could be converted to revenue due to capacity constraints. Flexibility shows increased value compared to a fixed design. However, when the system is allowed to upgrade too often, the costs of implementation negates the revenue increase. The better design is to have a high initial capacity, such that there is less restriction on the demand with two or three expansions.</jats:p
Differential Dynamics of Transposable Elements during Long-Term Diploidization of Nicotiana Section Repandae (Solanaceae) Allopolyploid Genomes
PubMed ID: 23185607This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
The phenomenological approach to modeling the dark energy
In this mini-review we discuss first why we should investigate cosmological
models beyond LCDM. We then show how to describe dark energy or modified
gravity models in a fluid language with the help of one background and two
perturbation quantities. We review a range of dark energy models and study how
they fit into the phenomenological framework, including generalizations like
phantom crossing, sound speeds different from c and non-zero anisotropic
stress, and how these effective quantities are linked to the underlying
physical models. We also discuss the limits of what can be measured with
cosmological data, and some challenges for the framework.Comment: 44 pages, 5 figures; accepted review article to appear in a special
volume of the "Comptes Rendus de l'Academie des Sciences" about Dark Energy
and Dark Matte
Fully nonlinear and exact perturbations of the Friedmann world model
In 1988 Bardeen has suggested a pragmatic formulation of cosmological
perturbation theory which is powerful in practice to employ various fundamental
gauge conditions easily depending on the character of the problem. The
perturbation equations are presented without fixing the temporal gauge
condition and are arranged so that one can easily impose fundamental gauge
conditions by simply setting one of the perturbation variables in the equations
equal to zero. In this way one can use the gauge degrees of freedom as an
advantage in handling problems. Except for the synchronous gauge condition, all
the other fundamental gauge conditions completely fix the gauge mode, and
consequently, each variable in such a gauge has a unique gauge invariant
counterpart, so that we can identify the variable as the gauge-invariant one.
Here, we extend Bardeen's linear formulation to fully nonlinear order in
perturbations, with the gauge advantage kept intact. Derived equations are
exact, and from these we can easily expand to higher order perturbations in a
gauge-ready form. We consider scalar- and vector-type perturbations of an ideal
fluid in a flat background; we also present the multiple components of ideal
fluid case. As applications we present fully nonlinear density and velocity
perturbation equations in Einstein's gravity in the zero-pressure medium,
vorticity generation from pure scalar-type perturbation, and fluid formulation
of a minimally coupled scalar field, all in the comoving gauge. We also present
the equation of gravitational waves generated from pure scalar- and vector-type
perturbations.Comment: 23 pages, to appear in MNRA
Barley plasma membrane intrinsic proteins (PIP aquaporins) as water and CO2 transporters
We identified barley aquaporins and demonstrated that one, HvPIP2;1, transports water and CO2. Regarding water homeostasis in plants, regulations of aquaporin expression were observed in many plants under several environmental stresses. Under salt stress, a number of plasma membrane-type aquaporins were down-regulated, which can prevent continuous dehydration resulting in cell death. The leaves of transgenic rice plants that expressed the largest amount of HvPIP2;1 showed a 40% increase in internal CO2 conductance compared with leaves of wild-type rice plants. The rate of CO2 assimilation also increased in the transgenic plants. The goal of our plant aquaporin research is to determine the key aquaporin species responsible for water and CO2 transport, and to improve plant water relations, stress tolerance, CO2 uptake or assimilation, and plant productivity via molecular breeding of aquaporins.</p
The synthesis, chain-packing simulation and long-term gas permeability of highly selective spirobifluorene-based polymers of intrinsic microporosity
Membranes composed of Polymers of Intrinsic Microporosity (SBF-PIMs) have potential for commercial gas separation. Here we report a combined simulation and experimental study to investigate the effect on polymer microporosity and gas permeability by placing simple substituents such as methyl, t-butyl and fused benzo groups onto PIMs derived from spirobifluorene (PIM-SBFs). It is shown that methyl or t-butyl substituents both cause a large increase in gas permeabilities with four methyl groups enhancing the concentration of ultramicropores (1.0 nm). Long-term ageing studies (>3.5 years) demonstrate the potential of PIM-SBFs as high-performance membrane materials for gas separations. In particular, the data for the PIM derived from tetramethyl substituted SBF reaches the proposed 2015 Robeson upper bound for O2/N2 and, hence, hold promise for the oxygen or nitrogen enrichment of air. Mixed gas permeation measurements for CO2/CH4 of the aged PIM-SBFs also demonstrate their potential for natural gas or biogas upgrading
The universe seen at different scales
A large-scale smoothed-out model of the universe ignores small-scale
inhomogeneities, but the averaged effects of those inhomogeneities may alter
both observational and dynamical relations at the larger scale. This article
discusses these effects, and comments briefly on the relation to gravitational
entropy.Comment: 17 pages; matches published version in Phys. Lett. A (Einstein
special issue
Corporate Social Responsibility and Islamic Financial Institutions (IFIs): Management Perceptions from IFIs in Bahrain
Islamic finance is gaining greater attention in the finance industry, and this paper analyses how Islamic financial institutions (IFIs) are responding to the welfare needs of society. Using interview data with managers and content analysis of the disclosures, this study attempts to understand management perceptions of corporate social
responsibility (CSR) in IFIs. A thorough understanding of CSR by managers, as evident in the interviews, has not been translated fully into practice. The partial use of IFIs’ potential role in social welfare would add further challenges in the era of financialisation
- …