Measuring Information Leakage using Generalized Gain Functions

International audienceThis paper introduces g-leakage, a rich general- ization of the min-entropy model of quantitative information flow. In g-leakage, the benefit that an adversary derives from a certain guess about a secret is specified using a gain function g. Gain functions allow a wide variety of operational scenarios to be modeled, including those where the adversary benefits from guessing a value close to the secret, guessing a part of the secret, guessing a property of the secret, or guessing the secret within some number of tries. We prove important properties of g-leakage, including bounds between min-capacity, g-capacity, and Shannon capacity. We also show a deep connection between a strong leakage ordering on two channels, C1 and C2, and the possibility of factoring C1 into C2 C3 , for some C3 . Based on this connection, we propose a generalization of the Lattice of Information from deterministic to probabilistic channels

Formation of the oxygen torus in the inner magnetosphere: Van Allen Probes observations

We study the formation process of an oxygen torus during the 12–15 November 2012 magnetic storm, using the magnetic field and plasma wave data obtained by Van Allen Probes. We estimate the local plasma mass density (ρL) and the local electron number density (neL) from the resonant frequencies of standing Alfvén waves and the upper hybrid resonance band. The average ion mass (M) can be calculated by M ∼ ρL/neL under the assumption of quasi-neutrality of plasma. During the storm recovery phase, both Probe A and Probe B observe the oxygen torus at L = 3.0–4.0 and L = 3.7–4.5, respectively, on the morning side. The oxygen torus has M = 4.5–8 amu and extends around the plasmapause that is identified at L∼3.2–3.9. We find that during the initial phase, M is 4–7 amu throughout the plasma trough and remains at ∼1 amu in the plasmasphere, implying that ionospheric O+ ions are supplied into the inner magnetosphere already in the initial phase of the magnetic storm. Numerical calculation under a decrease of the convection electric field reveals that some of thermal O+ ions distributed throughout the plasma trough are trapped within the expanded plasmasphere, whereas some of them drift around the plasmapause on the dawnside. This creates the oxygen torus spreading near the plasmapause, which is consistent with the Van Allen Probes observations. We conclude that the oxygen torus identified in this study favors the formation scenario of supplying O+ in the inner magnetosphere during the initial phase and subsequent drift during the recovery phase

Stoichiometric and Stable Isotope Ratios of Wild Lizards in an Urban Landscape Vary with Reproduction, Physiology, Space and Time

Spatial and temporal variation in stoichiometric and stable isotope ratios of animals contains ecological information that we are just beginning to understand. In both field and lab studies, stoichiometric or isotopic ratios are related to physiological mechanisms underlying nutrition or stress. Conservation and ecosystem ecology may be informed by isotopic data that can be rapidly and non-lethally collected from wild animals, especially where human activity leaves an isotopic signature (e.g. via introduction of chemical fertilizers, ornamental or other non-native plants or organic detritus). We examined spatial and temporal variation in stoichiometric and stable isotope ratios of the toes of Uta stansburiana (side-blotched lizards) living in urban and rural areas in and around St. George, Utah. We found substantial spatial and temporal variation as well as context-dependent co-variation with reproductive physiological parameters, although certain key predictions such as the relationship between δ15N and body condition were not supported. We suggest that landscape change through urbanization can have profound effects on wild animal physiology and that stoichiometric and stable isotope ratios can provide unique insights into the mechanisms underlying these processes

Reducing 3D MOC Storage Requirements with Axial On-the-fly Ray Tracing

The Method of Characteristics (MOC) is a popular method to solve the multi-group neutron transport equation. While this method is most widely used in two dimensions, extension to three dimensions allows for more accurate calculation of axial leakage and reaction rates. However, the 3D form of MOC can be computationally prohibitive. One concern is the massive memory requirements imposed by storing all segments of 3D tracks. In this study, an alternative approach is presented for axially extruded geometries that only saves segments in two dimensions. This is accomplished by first creating a 2D xy-plane that incorporates all radial detail at every axial level. Then, standard 2D ray tracing is applied to this plane. Axial extruded regions are constructed during segmentation, each containing an axial mesh. During transport sweeps the 3D segments are reconstructed on-the-fly using 2D segment lengths and 1D axial meshes. This strategy implicitly transforms geometries into an axially extruded representation. The resulting algorithm consumes far less memory with minimal computational overhead for common reactor physics problems.United States. Office of the Assistant Secretary for Nuclear Energy (Nuclear Energy University Programs Fellowship)Center for Exascale Simulation of Advanced Reactors (U.S. Department of Energy Contract No. DE-AC02-06CH11357

Verification of the 3D Method of characteristics solver in OpenMOC

The Method of Characteristics (MOC) has seen wide interest in full-core reactor physics analysis due to its computational efficiency and ability to easily treat complex geometries. Recently, the OpenMOC reactor physics code was extended to include 3D MOC capability. In this study, we present verification for the 3D MOC solver in OpenMOC and sensitivity of 3D MOC to the axial geometry discretization and axial track laydown. Results for the Takeda Model 1 benchmark show excellent agreement with the reference eigenvalues. A sensitivity study was conducted on a UO [subscript 2] quarter-assembly extracted from the C5G7 3D unrodded benchmark geometry in order to show the effect of the axial MOC parameters on the solution eigenvalue for a heterogeneous problem. The sensitivity results demonstrated that the solution accuracy was highly dependent on the axial source region discretization, but insensitive to axial spacing between tracks below ~0.2 cm. Using the equal angle quadrature set, at least 10 and 18 polar angles were required to converge the problem to with 100 and 10 pcm, respectively. These results both verify the 3D MOC solver in OpenMOC and provide inUnited States. Office of the Assistant Secretary for Nuclear Energy (Nuclear Energy Uni- versity Programs Fellowship)Center for Exascale Simulation of Advanced Reactors (Contract No. DE-AC02-06CH11357

Theoretical Analysis of Track Generation in 3d Method of Characteristics

Generating the tracks to use in a 3D Method of Characteristics (MOC) simulation is not a trivial task. The method used to generate tracks has significant implications on the memory and compute requirements for a problem and the current track generation methods have shortcomings. In this study, we provide a detailed description and analysis of the current state of the art method to generate tracks for direct 3D MOC, the Modular Ray Tracing (MRT) method. Additionally, a new global method for generating tracks is presented that is generalizable to many geometries, domain decomposition schemes, and quadrature sets. The main difference between the global and modular track generation approaches is that the global approach does not require any knowledge of the underlying geometry discretization and is therefore more flexible in domain decomposing the geometry. Some considerations with memory requirements and general applicability that we and others have found are discussedUnited States. Dept. of Energy. Office of Nuclear Energy (Nuclear Energy University Programs Fellowship)United States. Department of Energy (Center for Exascale Simulation of Advanced Reactors (CESAR). Contract DE-AC02-06CH11357

Mutations in modified virus Ankara protein 183 render it a non-functional counterpart of B14, an inhibitor of nuclear factor κB activation

Vaccinia virus (VACV) encodes multiple proteins to evade host innate immunity, including B14, a virulence factor that binds to the inhibitor of κB kinase β (IKKβ) and blocks nuclear factor κB (NF-κB) activation. B14 shares 95 % amino acid identity with the 183 protein encoded by modified virus Ankara (MVA), an attenuated VACV strain being developed as a vaccine vector. To evaluate whether the immunogenicity of MVA might be increased by manipulation of MVA immunomodulatory proteins, the MVA counterpart of B14, protein 183, was characterized. Unlike B14, protein 183 was unstable in eukaryotic cells unless proteasome-mediated protein degradation was inhibited. Furthermore, 183 did not inhibit NF-κB activation in response to cytokine stimulation, and did not restore the virulence of VACV strain Western Reserve lacking gene B14R. The instability and non-functionality of 183 are probably explained by a deletion of 6 aa within α-helix 6 of the B14 crystal structure

Evidence for Pre-Existing Dust in the Bright Type IIn SN 2010jl

SN 2010jl was an extremely bright, Type IIn SNe which showed a significant IR excess no later than 90 days after explosion. We have obtained Spitzer 3.6 and 4.5 \mum and JHK observations of SN 2010jl \sim90 days post explosion. Little to no reddening in the host galaxy indicated that the circumstellar material lost from the progenitor must lie in a torus inclined out of the plane of the sky. The likely cause of the high mid-IR flux is the reprocessing of the initial flash of the SN by pre-existing circumstellar dust. Using a 3D Monte Carlo Radiative Transfer code, we have estimated that between 0.03-0.35 Msun of dust exists in a circumstellar torus around the SN located 6 \times 10 ^17 cm away from the SN and inclined between 60-80\cdot to the plane of the sky. On day 90, we are only seeing the illumination of approximately 5% of this torus, and expect to see an elevated IR flux from this material up until day \sim 450. It is likely this dust was created in an LBV-like mass loss event of more than 3 Msun, which is large but consistent with other LBV progenitors such as {\eta} Carinae.Comment: Accepted in A