Properties of AGN coronae in the NuSTAR era

The focussing optics of NuSTAR have enabled high signal-to-noise spectra to be obtained from many X-ray bright Active Galactic Nuclei (AGN) and Galactic Black Hole Binaries (BHB). Spectral modelling then allows robust characterization of the spectral index and upper energy cutoff of the coronal power-law continuum, after accounting for reflection and absorption effects. Spectral-timing studies, such as reverberation and broad iron line fitting, of these sources yield coronal sizes, often showing them to be small and in the range of 3 to 10 gravitational radii in size. Our results indicate that coronae are hot and radiatively compact, lying close to the boundary of the region in the compactness - temperature diagram which is forbidden due to runaway pair production. The coincidence suggests that pair production and annihilation are essential ingredients in the coronae of AGN and BHB and that they control the shape of the observed spectra.Comment: 11 pages, 8 figures, accepted for publication in MNRA

Qualitative Factors in Organizational Cyber Resilience

Cyber resilience moves organizations away from efforts to guarantee security of all systems, towards an approach that acknowledges that systems are bound to fail with a focus instead on the impact of that failure on business objectives. While the work on cyber resilience is evolving, there is a lack of studies using qualitative data for investigating the concepts and themes pertaining to cyber resilience in organizations. The purpose of this study is to uncover the non-technical organizational factors that contribute to better cyber resilience. By adopting a qualitative approach of analyzing factors of organizational resilience, this paper uses primary data collected through 25 interviews at senior leadership or board-level to point out the extent to which these factors facilitate or impede cyber resilience. The study illustrates a Leximancer map of each factor that characterizes organizational cyber resilience, based on insights from cyber practitioner communities through narrative interviews. This research contributes to a better theoretical and practical understanding of how cyber resilience within organizations can be improved. The findings show that cyber strategy and skilled people playa key role in adoption of cyber culture at the management level, while communication between boards and security leadership as well as a clear reporting structure are signals for building cyber resilience

Particle Motion and Scalar Field Propagation in Myers-Perry Black Hole Spacetimes in All Dimensions

We study separability of the Hamilton-Jacobi and massive Klein-Gordon equations in the general Myers-Perry black hole background in all dimensions. Complete separation of both equations is carried out in cases when there are two sets of equal black hole rotation parameters, which significantly enlarges the rotational symmetry group. We explicitly construct a nontrivial irreducible Killing tensor associated with the enlarged symmetry group which permits separation. We also derive first-order equations of motion for particles in these backgrounds and examine some of their properties.Comment: 16 pages, LaTeX2

Glimmers: Resolving the Privacy/Trust Quagmire

Many successful services rely on trustworthy contributions from users. To establish that trust, such services often require access to privacy-sensitive information from users, thus creating a conflict between privacy and trust. Although it is likely impractical to expect both absolute privacy and trustworthiness at the same time, we argue that the current state of things, where individual privacy is usually sacrificed at the altar of trustworthy services, can be improved with a pragmatic $Glimmer$ $of$ $Trust$, which allows services to validate user contributions in a trustworthy way without forfeiting user privacy. We describe how trustworthy hardware such as Intel's SGX can be used client-side -- in contrast to much recent work exploring SGX in cloud services -- to realize the Glimmer architecture, and demonstrate how this realization is able to resolve the tension between privacy and trust in a variety of cases

Simple and Fast Biased Locks

Locks are used to ensure exclusive access to shared memory locations. Unfortunately, lock operations are expensive, so much work has been done on optimizing their performance for common access patterns. One such pattern is found in networking applications, where there is a single thread dominating lock accesses. An important special case arises when a single-threaded program calls a thread-safe library that uses locks. An effective way to optimize the dominant-thread pattern is to "bias" the lock implementation so that accesses by the dominant thread have negligible overhead. We take this approach in this work: we simplify and generalize existing techniques for biased locks, producing a large design space with many trade-offs. For example, if we assume the dominant process acquires the lock infinitely often (a reasonable assumption for packet processing), it is possible to make the dominant process perform a lock operation without expensive fence or compare-and-swap instructions. This gives a very low overhead solution; we confirm its efficacy by experiments. We show how these constructions can be extended for lock reservation, re-reservation, and to reader-writer situations

A Process Calculus for Dynamic Networks

In this paper we propose a process calculus framework for dynamic networks in which the network topology may change as computation proceeds. The proposed calculus allows one to abstract away from neighborhood-discovery computations and it contains features for broadcasting at multiple transmission ranges and for viewing networks at different levels of abstraction. We develop a theory of confluence for the calculus and we use the machinery developed towards the verification of a leader-election algorithm for mobile ad hoc networks

Prediction of storability of organically produced paddy seeds through natural and accelerated ageing techniques

The present study was conducted to know the storage potential of organically produced paddy seeds in the Department of Seed Science and Technology, University of Agricultural Sciences, Raichur. The seed lot were divided into two parts, one part was stored in cloth bag for a period of 12 months under ambient conditions. At thesame time another set of seeds were subjected to accelerated ageing at 42 + 10C temperature and 90 per cent relative humidity (RH) for a period of 0-12 days. Among the ageing methods, artificially aged seeds showed drastic decreases in seed quality as compared to natural ageing. Among the treatments T9 (37.5 % FYM + 37.5 % vermicompost + 25 % neem cake + foliar spray of panchagavya on 30, 60, 90 and 120 DAT) recorded significantly highest seed quality parameters viz., seed germination (97.81 %), seedling length (29.42 cm) and SVI (2878) at initial stage in both the method of aging and at the end of storage period; seed germination (71.23 and 87.33 %), seedling length (19.66 and 27.00 cm) and SVI (1400 and 2358) in accelerated ageing (AA) and natural ageing (NA) respectively, whereas, lowest in control (Inorganic treatment). The seed quality parameters of four days of AA were similar to that of six months of NA. Hence, storability of organically produced paddy seeds were better as compared to inorganic seeds and it can be predicted that four days of AA is equal to six months of NA. The information generated will be useful in retention or disposal of a particular variety or seed lot

Building Fuzzy Elevation Maps from a Ground-based 3D Laser Scan for Outdoor Mobile Robots

Mandow, A; Cantador, T.J.; Reina, A.J.; Martínez, J.L.; Morales, J.; García-Cerezo, A. "Building Fuzzy Elevation Maps from a Ground-based 3D Laser Scan for Outdoor Mobile Robots," Robot2015: Second Iberian Robotics Conference, Advances in Robotics, (2016) Advances in Intelligent Systems and Computing, vol. 418. This is a self-archiving copy of the author’s accepted manuscript. The final publication is available at Springer via http://link.springer.com/book/10.1007/978-3-319-27149-1.The paper addresses terrain modeling for mobile robots with fuzzy elevation maps by improving computational speed and performance over previous work on fuzzy terrain identification from a three-dimensional (3D) scan. To this end, spherical sub-sampling of the raw scan is proposed to select training data that does not filter out salient obstacles. Besides, rule structure is systematically defined by considering triangular sets with an unevenly distributed standard fuzzy partition and zero order Sugeno-type consequents. This structure, which favors a faster training time and reduces the number of rule parameters, also serves to compute a fuzzy reliability mask for the continuous fuzzy surface. The paper offers a case study using a Hokuyo-based 3D rangefinder to model terrain with and without outstanding obstacles. Performance regarding error and model size is compared favorably with respect to a solution that uses quadric-based surface simplification (QSlim).This work was partially supported by the Spanish CICYT project DPI 2011-22443, the Andalusian project PE-2010 TEP-6101, and Universidad de Málaga-Andalucía Tech

Toward a Multilevel Cognitive Probabilistic Representation of Space

This paper addresses the problem of perception and representation of space for a mobile agent. A probabilistic hierarchical framework is suggested as a solution to this problem. The method proposed is a combination of probabilistic belief with Object Graph Models(OGM). The world is viewed from a topological optic, in terms of objects and relationships between them. The hierarchical representation that we propose permits an efficient and reliable modeling of the information that the mobile agent would perceive from its environment. The integration of both navigational and interactional capabilities through efficient representation is also addressed. Experiments on a set of images taken from the real world that validate the approach are reported. This framework draws on the general understanding of human cognition and perception and contributes towards the overall efforts to build cognitive robot companions

Charges of Exceptionally Twisted Branes

The charges of the exceptionally twisted (D4 with triality and E6 with charge conjugation) D-branes of WZW models are determined from the microscopic/CFT point of view. The branes are labeled by twisted representations of the affine algebra, and their charge is determined to be the ground state multiplicity of the twisted representation. It is explicitly shown using Lie theory that the charge groups of these twisted branes are the same as those of the untwisted ones, confirming the macroscopic K-theoretic calculation. A key ingredient in our proof is that, surprisingly, the G2 and F4 Weyl dimensions see the simple currents of A2 and D4, respectively.Comment: 19 pages, 2 figures, LaTex2e, complete proofs of all statements, updated bibliograph