Are there any good digraph width measures?

Several different measures for digraph width have appeared in the last few years. However, none of them shares all the "nice" properties of treewidth: First, being \emph{algorithmically useful} i.e. admitting polynomial-time algorithms for all \MS1-definable problems on digraphs of bounded width. And, second, having nice \emph{structural properties} i.e. being monotone under taking subdigraphs and some form of arc contractions. As for the former, (undirected) \MS1 seems to be the least common denominator of all reasonably expressive logical languages on digraphs that can speak about the edge/arc relation on the vertex set.The latter property is a necessary condition for a width measure to be characterizable by some version of the cops-and-robber game characterizing the ordinary treewidth. Our main result is that \emph{any reasonable} algorithmically useful and structurally nice digraph measure cannot be substantially different from the treewidth of the underlying undirected graph. Moreover, we introduce \emph{directed topological minors} and argue that they are the weakest useful notion of minors for digraphs

Synchronizing Sequencing Software to a Live Drummer

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Temperature dependence of the phonon entropy of vanadium

The phonon density-of-states (DOS) of elemental vanadium was measured at elevated temperatures by inelastic neutron scattering. The phonon softening predicted by thermal expansion against the bulk modulus is much larger than the measured shifts in phonon energies. We conclude that the phonon anharmonicities associated with thermal expansion are largely canceled by effects from phonon-phonon scattering. Prior measurements of the heat capacity and calculations of the electronic entropy of vanadium are assessed, and consistency requires an explicit temperature dependence of the phonon DOS. Using data from the literature, similar results are found for chromium, niobium, titanium, and zirconium

Shock metamorphism of potassic feldspars

Hypervelocity meteorite impact produces transient pressures as high as several megabars and temperatures in excess of 1500 ºC. Shock metamorphism describes the effects upon the target rocks, effects most distinctive in the range approximately 100-600kb. Shock deformation produced in potassic feldspars at three terrestrial craters and in experimentally shocked K-spar have been examined. Pressures in natural material were estimated from deformation of coexisting quartz and plagioclase, and in experiments pressures were calculated using impedance matching. At Charlevoix crater, Quebec, pressures above 170kb have induced chemical remobilization partially converting film perthite to spindle microperthite in orthoclase and microcline. In ortho-clase, shock produced cleavages form parallel to (210) and (120) at 170kb, and above 300kb parallel to (ll2), (031), (Oil) and (101). Planar deformation features resulting from lattice gliding, form initially at 200kb, and are well developed at 230-270kb. In orthoclase they are generally parallel to (241) and (241), and (131), (110) and (120) in microcline. Above 300kb some sets become glide twins. Structural state of the feldspars is apparently not affected in the pressure range examined (≤ 360kb).In the breccias of Lac Couture crater, Quebec, strong deformation twins and planar features develop in microcline above ISOkb, and some of the twins may obey a 'diagonal' twin law. Single crystal microcline was experimentally shocked at pressures from 37 to 417kb. Three shock regions were recognized: Regime I (300kb) high pressure phase region. Shock cleavages, (111), (111) and (hkO), developed initially below 60kb, contain glass at highest pressures. Planar features, generally parallel to (111) and (111) also, appear at 154kb becoming more pronounced with increasing pressure, with poorly defined deformation twins occurring above 175kb. X-ray patterns show that long range structural order diminishes above ISOkb accompanied by formation of a low-birefringent, unidentified phase, possibly a high-pressure, disordered modification of K-feldspar. Differences in the pressure required for formation of particular shock effects between craters, and between natural and experimental systems are due to differences in structural state of the feldspars. At Brent crater, Ontario, partially recrystallized alkali feldspars in shocked basement gneisses show compositional variations due to incomplete homogenization. This is not a shock effect but results from thermal metamorphism by the overlying melt layer. A similar thermal effect has produced chemical variations in some highly shocked orthoclases at Charlevoix

Ionisation and discharge in cloud-forming atmospheres of brown dwarfs and extrasolar planets

Brown dwarfs and giant gas extrasolar planets have cold atmospheres with rich chemical compositions from which mineral cloud particles form. Their properties, like particle sizes and material composition, vary with height, and the mineral cloud particles are charged due to triboelectric processes in such dynamic atmospheres. The dynamics of the atmospheric gas is driven by the irradiating host star and/or by the rotation of the objects that changes during its lifetime. Thermal gas ionisation in these ultra-cool but dense atmospheres allows electrostatic interactions and magnetic coupling of a substantial atmosphere volume. Combined with a strong magnetic field , a chromosphere and aurorae might form as suggested by radio and x-ray observations of brown dwarfs. Non-equilibrium processes like cosmic ray ionisation and discharge processes in clouds will increase the local pool of free electrons in the gas. Cosmic rays and lighting discharges also alter the composition of the local atmospheric gas such that tracer molecules might be identified. Cosmic rays affect the atmosphere through air showers in a certain volume which was modelled with a 3D Monte Carlo radiative transfer code to be able to visualise their spacial extent. Given a certain degree of thermal ionisation of the atmospheric gas, we suggest that electron attachment to charge mineral cloud particles is too inefficient to cause an electrostatic disruption of the cloud particles. Cloud particles will therefore not be destroyed by Coulomb explosion for the local temperature in the collisional dominated brown dwarf and giant gas planet atmospheres. However, the cloud particles are destroyed electrostatically in regions with strong gas ionisation. The potential size of such cloud holes would, however, be too small and might occur too far inside the cloud to mimic the effect of, e.g. magnetic field induced star spots

Brood patch and sex-ratio observations indicate breeding provenance and timing in New Zealand storm petrel (Fregetta maoriana)

We used measurements of brood patch and moult status to estimate the breeding phenology of New Zealand Storm-Petrel, using birds caught at sea within the Hauraki Gulf Marine Park near Auckland, New Zealand. Birds caught October–January had completely downy brood patches, whereas birds caught February–April had bare brood patches with an observed male bias in the February sex-ratio, consistent with a female pre-laying exodus typical of petrels and with the existence of an unknown colony in the region. No birds captured exhibited primary moult, which is known to occur in storm-petrels during their non-breeding season. Our data support the conclusion that the New Zealand storm-petrel breeds during January–June in northern New Zealand and that field surveys for the species on offshore islands in this region during this period are warrante

Transport theory yields renormalization group equations

We show that dissipative transport and renormalization can be described in a single theoretical framework. The appropriate mathematical tool is the Nakajima-Zwanzig projection technique. We illustrate our result in the case of interacting quantum gases, where we use the Nakajima-Zwanzig approach to investigate the renormalization group flow of the effective two-body interaction.Comment: 11 pages REVTeX, twocolumn, no figures; revised version with additional examples, to appear in Phys. Rev.

A New Approach to Time Domain Classification of Broadband Noise in Gravitational Wave Data

Broadband noise in gravitational wave (GW) detectors, also known as triggers, can often be a deterrant to the efficiency with which astrophysical search pipelines detect sources. It is important to understand their instrumental or environmental origin so that they could be eliminated or accounted for in the data. Since the number of triggers is large, data mining approaches such as clustering and classification are useful tools for this task. Classification of triggers based on a handful of discrete properties has been done in the past. A rich information content is available in the waveform or 'shape' of the triggers that has had a rather restricted exploration so far. This paper presents a new way to classify triggers deriving information from both trigger waveforms as well as their discrete physical properties using a sequential combination of the Longest Common Sub-Sequence (LCSS) and LCSS coupled with Fast Time Series Evaluation (FTSE) for waveform classification and the multidimensional hierarchical classification (MHC) analysis for the grouping based on physical properties. A generalized k-means algorithm is used with the LCSS (and LCSS+FTSE) for clustering the triggers using a validity measure to determine the correct number of clusters in absence of any prior knowledge. The results have been demonstrated by simulations and by application to a segment of real LIGO data from the sixth science run.Comment: 16 pages, 16 figure

CANLEX (Canadian Liquefaction Experiment): A One Year Update

The Canadian Geotechnical engineering community has embarked on a major study regarding the liquefaction of sand entitled The Canadian Liquefaction Experiment (CANLEX) through a collaborative effort of industry, engineering consultants and university participants, with the support of the Natural Sciences and Engineering Research Council of Canada (NSERC). The study is examining the characterization of sand for dynamic and static liquefaction. The project was started in 1993 and is expected to last at least 3 years with equal funding by both industry and NSERC for a total of about C$1.8M. This paper provides a brief progress report on the Project. Three test sites have been selected and characterized using in-situ testing, conventional sampling as well as in-situ freezing to obtain undisturbed samples. Laboratory testing is underway on both reconstituted samples and undisturbed samples. A full scale liquefaction event is planned for year three of the Project and a feasibility study regarding the event has been completed. As part of the planning for the liquefaction event some preliminary centrifuge testing has been carried out. A static liquefaction flow failure has been successfully produced in the centrifuge. As part of the Project, a set of definitions for liquefaction have been defined and a flow chart developed to aid in the liquefaction analyses

On the Monadic Second-Order Transduction Hierarchy

We compare classes of finite relational structures via monadic second-order transductions. More precisely, we study the preorder where we set C \subseteq K if, and only if, there exists a transduction {\tau} such that C\subseteq{\tau}(K). If we only consider classes of incidence structures we can completely describe the resulting hierarchy. It is linear of order type {\omega}+3. Each level can be characterised in terms of a suitable variant of tree-width. Canonical representatives of the various levels are: the class of all trees of height n, for each n \in N, of all paths, of all trees, and of all grids