The flask security architecture: system support for diverse security policies

technical reportOperating systems must be flexible in their support for security policies, i.e., the operating system must provide sufficient mechanisms for supporting the wide variety of real-world security policies. Systems claiming to provide this support have failed to do so in two ways: they either fail to provide sufficient control over the propagation of access rights, or they fail to provide enforcement mechanisms to support fine-grained control and dynamic security policies. In this paper we present an operating systems security architecture that solves both of these problems. The first problem is solved by ensuring that the security policy (through a consistent replica) is consulted for every security decision. The second problem is solved through mechanisms that are directly integrated into the service-providing components of the system. The architecture is described through its prototype implementation in the Flask microkernel-based OS, and the policy flexibility of the prototype is evaluated. We present initial evidence that the architecture's performance impact is modest. Moreover, our architecture is applicable to many other types of operating systems and environments

Discovery of a Visual T-Dwarf Triple System and Binarity at the L/T Transition

We present new high contrast imaging of 8 L/T transition brown dwarfs using the NIRC2 camera on the Keck II telescope. One of our targets, the T3.5 dwarf 2MASS J08381155 + 1511155, was resolved into a hierarchal triple with projected separations of 2.5+/-0.5 AU and 27+/-5 AU for the BC and A(BC) components respectively. Resolved OSIRIS spectroscopy of the A(BC) components confirm that all system members are T dwarfs. The system therefore constitutes the first triple T-dwarf system ever reported. Using resolved photometry to model the integrated-light spectrum, we infer spectral types of T3, T3, and T4.5 for the A, B, and C components respectively. The uniformly brighter primary has a bluer J-Ks color than the next faintest component, which may reflect a sensitive dependence of the L/T transition temperature on gravity, or alternatively divergent cloud properties amongst components. Relying on empirical trends and evolutionary models we infer a total system mass of 0.034-0.104 Msun for the BC components at ages of 0.3-3 Gyr, which would imply a period of 12-21 yr assuming the system semi-major axis to be similar to its projection. We also infer differences in effective temperatures and surface gravities between components of no more than ~150 K and ~0.1 dex. Given the similar physical properties of the components, the 2M0838+15 system provides a controlled sample for constraining the relative roles of effective temperature, surface gravity, and dust clouds in the poorly understood L/T transition regime. Combining our imaging survey results with previous work we find an observed binary fraction of 4/18 or 22_{-8}^{+10}% for unresolved spectral types of L9-T4 at separations >~0.1 arcsec. This translates into a volume-corrected frequency of 13^{-6}_{+7}%, which is similar to values of ~9-12% reported outside the transition. (ABRIDGED)Comment: Accepted for publication in the Astrophysical Journal. 23 pages, 12 figure

The 2HA line of Medicago truncatula has characteristics of an epigenetic mutant that is weakly ethylene insensitive

BACKGROUND The Medicago truncatula 2HA seed line is highly embryogenic while the parental line Jemalong rarely produces embryos. The 2HA line was developed from one of the rare Jemalong regenerates and this method for obtaining a highly regenerable genotype in M. truncatula is readily reproducible suggesting an epigenetic mechanism. Microarray transcriptomic analysis showed down regulation of an ETHYLENE INSENSITIVE 3-like gene in 2HA callus which provided an approach to investigating epigenetic regulation of genes related to ethylene signalling and the 2HA phenotype. Ethylene is involved in many developmental processes including somatic embryogenesis (SE) and is associated with stress responses. RESULTS Microarray transcriptomic analysis showed a significant number of up-regulated transcripts in 2HA tissue culture, including nodule and embryo specific genes and transposon-like genes, while only a few genes were down-regulated, including an EIN3-like gene we called MtEIL1. This reduced expression was associated with ethylene insensitivity of 2HA plants that was further investigated. The weak ethylene insensitivity affected root and nodule development. Sequencing of MtEIL1 found no difference between 2HA and wild-type plants. DNA methylation analysis of MtEIL1 revealed significant difference between 2HA and wild-type plants. Tiling arrays demonstrated an elevated level of miRNA in 2HA plants that hybridised to the antisense strand of the MtEIL1 gene. AFLP-like methylation profiling revealed more differences in DNA methylation between 2HA and wild-type. Segregation analysis demonstrated the recessive nature of the eil1 phenotype and the dominant nature of the SE trait. CONCLUSIONS We have demonstrated that EIL1 of Medicago truncatula (MtEIL1) is epigenetically silenced in the 2HA seed line. The possible cause is an elevated level of miRNA that targets its 3'UTR and is also associated with DNA methylation of MtEIL1. Down regulation of MtEIL1 makes it possible to form nodules in the presence of ethylene and affects root growth under normal conditions. Segregation analysis showed no association between MtEIL1 expression and SE in culture but the role and mechanism of ethylene signalling in the process of plant regeneration through SE requires further investigation. The work also suggests that epigenetic changes to a particular gene induced in culture can be fixed in regenerated plants.This work was funded by the Australian Research Council (CEO348212) through the ARC Centre of Excellence for Integrative Legume Research (CILR)

\u3cem\u3eColemanus keeleyorum\u3c/em\u3e (Braconidae, Ichneutinae s. l.): A New Genus and Species of Eocene Wasp From the Green River Formation of Western North America

A new genus and species of Ichneutinae s. l., Colemanus keeleyorum Fisher, is described from the Eocene Green River Formation in Colorado, USA. Colemanus was placed on a phylogenetic hypothesis using morphological data. Using a parsimony criterion, Colemanus is placed within Proteropini (Ichneutinae s. l.). Reconstructions of well-preserved regions (mesosomal dorsum and wings) are included. A previously described species from lower Oligocene Baltic amber is transferred to Colemanus, resulting in the new combination C. contortus (Brues, 1933)

\u3cem\u3eColemanus keeleyorum\u3c/em\u3e (Braconidae, Ichneutinae s. l.): A New Genus and Species of Eocene Wasp From the Green River Formation of Western North America

A new genus and species of Ichneutinae s. l., Colemanus keeleyorum Fisher, is described from the Eocene Green River Formation in Colorado, USA. Colemanus was placed on a phylogenetic hypothesis using morphological data. Using a parsimony criterion, Colemanus is placed within Proteropini (Ichneutinae s. l.). Reconstructions of well-preserved regions (mesosomal dorsum and wings) are included. A previously described species from lower Oligocene Baltic amber is transferred to Colemanus, resulting in the new combination C. contortus (Brues, 1933)

Rates and Intermediates in Ser26 Mutants of Benzoylformate Decarboxylase

poster abstractBenzoylformate decarboxylase (BFDC), a thiamine diphosphate dependent enzyme, catalyzes decarboxylation of benzoylformate to benzaldehyde and CO2. The BFDC reaction proceeds through at least four individual chemical steps and, recently, NMR spectroscopy has been used to measure the ratios of intermediates in the overall reaction. This method permits calculation of rate constants for formation of the first intermediate, mandelylThDP (k2) and its subsequent decarboxylation (k3), as well as the combined breakdown of the enamine and product release (k4). As part of a study of the contributions of the active site residues, Ser26, His70 and His281, to the individual catalytic steps several Ser26 variants were expressed and purified. Initially, the variants were characterized using steady-state kinetics. Subsequently, the enzymes were mixed with benzoylformate and the mixture immediately acid quenched to trap intermediates of the reaction. NMR spectroscopy was used to identify and quantitate individual catalytic intermediates. Rate constants for the formation of these intermediates were then determined and compared to those of the wild-type enzyme. Here we report those results and discuss their implications for the role of Ser26 in the BFDC reaction mechanism

Silicate Emission in the TW Hydrae Association

The TW Hydrae Association is the nearest young stellar association. Among its members are HD 98800, HR 4796A, and TW Hydrae itself, the nearest known classical T Tauri star. We have observed these three stars spectroscopically between 3 and 13 microns. In TW Hya the spectrum shows a silicate emission feature that is similar to many other young stars with protostellar disks. The 11.2 micron feature indicative of significant amounts of crystalline olivine is not as strong as in some young stars and solar system comets. In HR 4796A, the thermal emission in the silicate feature is very weak, suggesting little in the way of (small silicate) grains near the star. The silicate band of HD 98800 (observed by us but also reported by Sylvester and Skinner (1996)) is intermediate in strength between TW Hya and HR 4796.Comment: 22 pages, 11 figures, LaTeX2e and AAS LaTeX macros v5.0. Accepted for publication in A

Resolving the gap and AU-scale asymmetries in the pre-transitional disk of V1247 Orionis

Pre-transitional disks are protoplanetary disks with a gapped disk structure, potentially indicating the presence of young planets in these systems. In order to explore the structure of these objects and their gap-opening mechanism, we observed the pre-transitional disk V1247 Orionis using the Very Large Telescope Interferometer, the Keck Interferometer, Keck-II, Gemini South, and IRTF. This allows us spatially resolve the AU-scale disk structure from near- to mid-infrared wavelengths (1.5 to 13 {\mu}m), tracing material at different temperatures and over a wide range of stellocentric radii. Our observations reveal a narrow, optically-thick inner-disk component (located at 0.18 AU from the star) that is separated from the optically thick outer disk (radii >46 AU), providing unambiguous evidence for the existence of a gap in this pre-transitional disk. Surprisingly, we find that the gap region is filled with significant amounts of optically thin material with a carbon-dominated dust mineralogy. The presence of this optically thin gap material cannot be deduced solely from the spectral energy distribution, yet it is the dominant contributor at mid-infrared wavelengths. Furthermore, using Keck/NIRC2 aperture masking observations in the H, K', and L' band, we detect asymmetries in the brightness distribution on scales of about 15-40 AU, i.e. within the gap region. The detected asymmetries are highly significant, yet their amplitude and direction changes with wavelength, which is not consistent with a companion interpretation but indicates an inhomogeneous distribution of the gap material. We interpret this as strong evidence for the presence of complex density structures, possibly reflecting the dynamical interaction of the disk material with sub-stellar mass bodies that are responsible for the gap clearing.Comment: 16 pages, 17 Figures, accepted by Astrophysical Journa