Pairs of Languages Closed under Shuffle Projection

Shuffle projection is motivated by the verification of safety properties of special parameterized systems. Basic definitions and properties, especially related to alphabetic homomorphisms, are presented. The relation between iterated shuffle products and shuffle projections is shown. A special class of multi-counter automata is introduced, to formulate shuffle projection in terms of computations of these automata represented by transductions. This reformulation of shuffle projection leads to construction principles for pairs of languages closed under shuffle projection. Additionally, it is shown that under certain conditions these transductions are rational, which implies decidability of closure against shuffle projection. Decidability of these conditions is proven for regular languages. Finally, without additional conditions, decidability of the question, whether a pair of regular languages is closed under shuffle projection, is shown. In an appendix the relation between shuffle projection and the shuffle product of two languages is discussed. Additionally, a kind of shuffle product for computations in S-automata is defined

Security Analysis of System Behaviour - From "Security by Design" to "Security at Runtime" -

The Internet today provides the environment for novel applications and processes which may evolve way beyond pre-planned scope and purpose. Security analysis is growing in complexity with the increase in functionality, connectivity, and dynamics of current electronic business processes. Technical processes within critical infrastructures also have to cope with these developments. To tackle the complexity of the security analysis, the application of models is becoming standard practice. However, model-based support for security analysis is not only needed in pre-operational phases but also during process execution, in order to provide situational security awareness at runtime. This cumulative thesis provides three major contributions to modelling methodology. Firstly, this thesis provides an approach for model-based analysis and verification of security and safety properties in order to support fault prevention and fault removal in system design or redesign. Furthermore, some construction principles for the design of well-behaved scalable systems are given. The second topic is the analysis of the exposition of vulnerabilities in the software components of networked systems to exploitation by internal or external threats. This kind of fault forecasting allows the security assessment of alternative system configurations and security policies. Validation and deployment of security policies that minimise the attack surface can now improve fault tolerance and mitigate the impact of successful attacks. Thirdly, the approach is extended to runtime applicability. An observing system monitors an event stream from the observed system with the aim to detect faults - deviations from the specified behaviour or security compliance violations - at runtime. Furthermore, knowledge about the expected behaviour given by an operational model is used to predict faults in the near future. Building on this, a holistic security management strategy is proposed. The architecture of the observing system is described and the applicability of model-based security analysis at runtime is demonstrated utilising processes from several industrial scenarios. The results of this cumulative thesis are provided by 19 selected peer-reviewed papers

T2-based temperature monitoring in bone marrow for MR-guided focused ultrasound.

BackgroundCurrent clinical protocols for MR-guided focused ultrasound (MRgFUS) treatment of osseous lesions, including painful bone metastases and osteoid osteomas, rely on measurement of the temperature change in adjacent muscle to estimate the temperature of the bone. The goal of this study was to determine if T2-based thermometry could be used to monitor the temperature change in bone marrow during focused ultrasound ablation of bone lesions.MethodsWe investigated the dependence of T2 on temperature in ex vivo bovine yellow bone marrow at 3T and studied the influence of acquisition parameters on the T2 measurements. We examined if T2 changes in red bone marrow caused by the ablation of ex vivo trabecular bone were reversible and measured the patterns of heating and tissue damage. The technique was validated during the ablation of intact ex vivo bone samples and an in vivo animal model.ResultsResults of the calibration experiment showed a linear relationship (7 ms/°C) between T2 change and temperature and could be used to quantify the temperature during heating of up to 60 °C. During trabecular bone ablation, we observed a linear relationship (5.7 ms per °C) between T2 and temperature during the heating stage of the experiment. After cool down, there was residual T2 elevation (~35 ms) in the ablated area suggesting irreversible tissue changes. In ex vivo and in vivo cortical bone ablation experiments, we observed an increase in T2 values in the marrow adjacent to the intersection of the cortical bone and the beam path. The in vivo experiment showed excellent correspondence between the area of T2 elevation in marrow during the ablation and the resulting non-enhancing area in the post-contrast images.ConclusionsIn this study, we have demonstrated that T2-based thermometry can be used in vivo to measure the heating in the marrow during bone ablation. The ability to monitor the temperature within the bone marrow allowed more complete visualization of the heat distribution into the bone, which is important for local lesion control

Modelling and analysing network security policies in a given vulnerability setting

Abstract. The systematic protection of critical information infrastructures requires an analytical process to identify the critical components and their interplay, to determine the threats and vulnerabilities, to assess the risks and to prioritise countermeasures where risk is unacceptable. This paper presents an integrated framework for model-based symbolic interpretation, simulation and analysis with a comprehensive approach focussing on the validation of network security policies. A graph of all possible attack paths is automatically computed from the model of an ICT network, of vulnerabilities, exploits and an attacker strategy. Constraints on this graph are given by a model of the network security policy. The impact of changes to security policies can be computed and visualised by finding differences in the attack graphs. A unique feature of the presented approach is, that abstract representations of these graphs can be computed that allow comparison of focussed views on the behaviour of the system. This guides optimal adaptation of the security policy to the given vulnerability setting

Security properties of self-similar uniformly parameterised systems of cooperations

Abstract-Uniform parameterisations of cooperations are defined in terms of formal language theory, such that each pair of partners cooperates in the same manner, and that the mechanism (schedule) to determine how one partner may be involved in several cooperations, is the same for each partner. Generalising each pair of partners cooperating in the same manner, for such systems of cooperations a kind of selfsimilarity is formalised. From an abstracting point of view, where only actions of some selected partners are considered, the complex system of all partners behaves like the smaller subsystem of the selected partners. For verification purposes, so called uniformly parameterised safety properties are defined. Such properties can be used to express privacy policies as well as security and dependability requirements. It is shown, how the parameterised problem of verifying such a property is reduced by self-similarity to a finite state problem. Keywords-cooperations as prefix closed languages; abstractions of system behaviour; self-similarity in systems of cooperations; privacy policies; uniformly parameterised safety properties

NICMOS Imaging of the HR 4796A Circumstellar Disk

We report the first near infrared (NIR) imaging of a circumstellar annular disk around the young (~8 Myr), Vega-like star, HR 4796A. NICMOS coronagraph observations at 1.1 and 1.6 microns reveal a ring-like symmetrical structure peaking in reflected intensity 1.05 arcsec +/- 0.02 arcsec (~ 70 AU) from the central A0V star. The ring geometry, with an inclination of 73.1 deg +/- 1.2 deg and a major axis PA of 26.8 deg +/- 0.6 deg, is in good agreement with recent 12.5 and 20.8 micron observations of a truncated disk (Koerner, et al. 1998). The ring is resolved with a characteristic width of less than 0.26 arcsec (17 AU) and appears abruptly truncated at both the inner and outer edges. The region of the disk-plane inward of ~60 AU appears to be relatively free of scattering material. The integrated flux density of the part of the disk that is visible (greater than 0.65 arcsec from the star) is found to be 7.5 +/- 0.5 mJy and 7.4 +/- 1.2 mJy at 1.1 and 1.6 microns, respectively. Correcting for the unseen area of the ring yields total flux densities of 12.8 +/- 1.0 mJy and 12.5 +/- 2.0 mJy, respectively (Vega magnitudes = 12.92 /+- 0.08 and 12.35 +/-0.18). The NIR luminosity ratio is evaluated from these results and ground-based photometry of the star. At these wavelengths Ldisk(lambda)/L*(lambda) = 1.4 +/- 0.2E-3 and 2.4 +/- 0.5E-3, giving reasonable agreement between the stellar flux scattered in the NIR and that which is absorbed in the visible and re-radiated in the thermal infrared. The somewhat red reflectance of the disk at these wavelengths implies mean particle sizes in excess of several microns, larger than typical interstellar grains. The confinement of material to a relatively narrow annular zone implies dynamical constraints on the disk particles by one or more as yet unseen bodies.Comment: 14 pages, 1 figure for associated gif file see: http://nicmosis.as.arizona.edu:8000/AAS99/FIGURE1_HR4796A_ApJL.gif . Accepted 13 January 1999, Astrophyical Journal Letter

Cyberattack Detection in Vehicles using Characteristic Functions, Artificial Neural Networks, and Visual Analysis

The connectivity of autonomous vehicles induces new attack surfaces and thus the demand for sophisticated cybersecurity management. Thus, it is important to ensure that in-vehicle network monitoring includes the ability to accurately detect intrusive behavior and analyze cyberattacks from vehicle data and vehicle logs in a privacy-friendly manner. For this purpose, we describe and evaluate a method that utilizes characteristic functions and compare it with an approach based on artificial neural networks. Visual analysis of the respective event streams complements the evaluation. Although the characteristic functions method is an order of magnitude faster, the accuracy of the results obtained is at least comparable to those obtained with the artificial neural network. Thus, this method is an interesting option for implementation in in-vehicle embedded systems. An important aspect for the usage of the analysis methods within a cybersecurity framework is the explainability of the detection results

Asteroid Distributions in the Ecliptic

We present analysis of the asteroid surface density distribution of main belt asteroids (mean perihelion $\Delta \simeq 2.404$ AU) in five ecliptic latitude fields, -17 \gtsimeq \beta(\degr) \ltsimeq +15, derived from deep \textit{Large Binocular Telescope} (LBT) $V-$band (85% completeness limit $V = 21.3$ mag) and \textit{Spitzer Space Telescope} IRAC 8.0 \micron (80% completeness limit $\sim 103 \mu$Jy) fields enabling us to probe the 0.5--1.0 km diameter asteroid population. We discovered 58 new asteroids in the optical survey as well as 41 new bodies in the \textit{Spitzer} fields. The derived power law slopes of the number of asteroids per square degree are similar within each $\sim 5$\degr{} ecliptic latitude bin with a mean value of $-0.111 \pm 0.077$. For the 23 known asteroids detected in all four IRAC channels mean albedos range from $0.24 \pm 0.07$ to $0.10 \pm 0.05$. No low albedo asteroids ($p_{V}$ \ltsimeq 0.1) were detected in the \textit{Spitzer} FLS fields, whereas in the SWIRE fields they are frequent. The SWIRE data clearly samples asteroids in the middle and outer belts providing the first estimates of these km-sized asteroids' albedos. Our observed asteroid number densities at optical wavelengths are generally consistent with those derived from the Standard Asteroid Model within the ecliptic plane. However, we find an over density at \beta \gtsimeq 5\degr{} in our optical fields, while the infrared number densities are under dense by factors of 2 to 3 at all ecliptic latitudes.Comment: 35 pages including 5 figures, accepted to The Astronomical Journa

Microvariability in the optical polarization of 3C279

We present results of a microvariability polarization study in the violently variable quasar 3C279. We have resolved the polarization curves in the V band for this object down to timescales of minutes. We found two main components in the evolution of the degree of linear polarization, one consisting of a flicker with timescales of several tens of minutes and other component with far more significant variations on timescales of a few days. The linear polarization descended from $\sim 17$ % down to $\sim 8$ % in three nights. The polarization angle underwent a sudden change of more that 10 degrees in a few hours, perhaps indicating the injection of a new shock in the jet. The amplitude of the intranight flickering in the degree of polarization is at the level of $\sim 1$%. These are probably the best sampled polarization data ever obtained for this object. We also performed IR observations and we provide a follow-up of the evolution of this source at such energies after the main polarization outburst.Comment: 10 pages, 9 figures, accepted for publication in A&

GM 2-4 - a signpost for low and intermediate mass star formation

We present a multi-wavelength study of the region towards the GM 2-4 nebula and the nearby source IRAS 05373+2340. Our near-infrared H2 1-0 S(1) line observations reveal various shock-excited features which are part of several bipolar outflows. We identify candidates for the driving sources of the outflows from a comparison of the multi-waveband archival data-sets and SED modelling. The SED spectral slope (\alpha(IRAC)) for all the protostars in the field was then compared with the visual extinction map. This comparison suggests that star formation is progressing from NE to SW across this region