5,445 research outputs found
Updated geometry description for the LHCb Trigger Tracker
The XML based detector description for the Trigger Tracker (TT) station has been updated. A more realistic version has been implemented in which volumes for frames, readout cables, balconies, jackets, cooling plates and elements have been added in addition to a detailed description of the detector modules. In this note an overview of the updated description is presented
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Provisions for oil and gas decommissioning costs: compliance with disclosure requirements by oil and gas companies listed in the UK
Due to their complications in terms of uncertainty and calculations provisions for oil and gas decommissioning costs are not easy to be understood and interpret by users of no accounting and finance background. Furthermore, due to their significant sizes, cash outflow effect and importance for decision making disclosing more detailed information seem to be ideal requirement to simplify these complications. This study raises, almost for the first time, queries about compliance, sufficiency, uniformity and fairness of oil and gas companies' disclosure practices with regard to provisions for decommissioning costs. In order to provide answers to the research quires, annual reports of 69 oil and gas companies listed in the UK were analysed and thirteen interviews with different professionals were conducted. Our results reveal that whilst there is sufficient standards to regulate accounting for provisions for decommissioning costs there seems to be lack of compliance with requirements of international accounting standards in terms of disclosing information on provisions for decommissioning costs. In many cases, and probably due to their sensitive nature, we found that oil and gas companies tend to disclose a minimum amount of information about provisions for decommissioning costs
New waterboatmen records for Western Canada (Hemiptera: Corixidae)
Trichocorixa verticalis (Fieber) is reported for the first time from the mainland of British Columbia and the subspecific assignment is discussed. Based on specimens in the Spencer Entomological Museum, one provincial record and one territorial record are added to the recent checklist of Canadian Hemiptera
Applicability and Utility of the Astromaterials X-Ray Computed Tomography Laboratory at Johnson Space Center
The Astromaterials Acquisition and Curation Office at NASAs Johnson Space Center is responsible for curating all of NASAs astromaterial sample collections (i.e. Apollo samples, Luna Samples, Antarctic Meteorites, Cosmic Dust Particles, Microparticle Impact Collection, Genesis solar wind atoms, Stardust comet Wild-2 particles, Stardust interstellar particles, and Hayabusa asteroid Itokawa particles) [1-3]. To assist in sample curation and distribution, JSC Curation has recently installed an X-ray computed tomography (XCT) scanner to visualize and characterize samples in 3D. [3] describes the instrumental set-up and the utility of XCT to astromaterials curation. Here we describe some of the current and future projects and illustrate the usefulness of XCT in studying astromaterials
Proof Theory, Transformations, and Logic Programming for Debugging Security Protocols
We define a sequent calculus to formally specify, simulate, debug and verify security protocols. In our sequents we distinguish between the current knowledge of principals and the current global state of the session. Hereby, we can describe the operational semantics of principals and of an intruder in a simple and modular way. Furthermore, using proof theoretic tools like the analysis of permutability of rules, we are able to find efficient proof strategies that we prove complete for special classes of security protocols including Needham-Schroeder. Based on the results of this preliminary analysis, we have implemented a Prolog meta-interpreter which allows for rapid prototyping and for checking safety properties of security protocols, and we have applied it for finding error traces and proving correctness of practical examples
Diffusion-Limited Aggregation on Curved Surfaces
We develop a general theory of transport-limited aggregation phenomena
occurring on curved surfaces, based on stochastic iterated conformal maps and
conformal projections to the complex plane. To illustrate the theory, we use
stereographic projections to simulate diffusion-limited-aggregation (DLA) on
surfaces of constant Gaussian curvature, including the sphere () and
pseudo-sphere (), which approximate "bumps" and "saddles" in smooth
surfaces, respectively. Although curvature affects the global morphology of the
aggregates, the fractal dimension (in the curved metric) is remarkably
insensitive to curvature, as long as the particle size is much smaller than the
radius of curvature. We conjecture that all aggregates grown by conformally
invariant transport on curved surfaces have the same fractal dimension as DLA
in the plane. Our simulations suggest, however, that the multifractal
dimensions increase from hyperbolic () geometry, which
we attribute to curvature-dependent screening of tip branching.Comment: 4 pages, 3 fig
Altered Cerebellar Short-Term Plasticity but No Change in Postsynaptic AMPA-Type Glutamate Receptors in a Mouse Model of Juvenile Batten Disease
Juvenile Batten disease is the most common progressive neurodegenerative disorder of childhood. It is associated with mutations in the CLN3 gene, causing loss of function of CLN3 protein and degeneration of cerebellar and retinal neurons. It has been proposed that changes in granule cell AMPA-type glutamate receptors (AMPARs) contribute to the cerebellar dysfunction. In this study we compared AMPAR properties and synaptic transmission in cerebellar granule cells from wild-type and Cln3 knockout mice. In Cln3Δex1–6 cells the amplitude of AMPA-evoked whole-cell currents was unchanged. Similarly, we found no change in the amplitude, kinetics, or rectification of synaptic currents evoked by individual quanta, or in their underlying single-channel conductance. We found no change in cerebellar expression of GluA2 or GluA4 protein. By contrast, we observed a reduced number of quantal events following mossy-fiber stimulation in Sr2+, altered short-term plasticity in conditions of reduced extracellular Ca2+, and reduced mossy fiber vesicle number. Thus, while our results suggest early presynaptic changes in the Cln3Δex1–6 mouse model of juvenile Batten disease, they reveal no evidence for altered postsynaptic AMPARs
The initial development of a jet caused by fluid, body and free surface interaction with a uniformly accelerated advancing or retreating plate. Part 1. The principal flow
The free surface and flow field structure generated by the uniform acceleration (with dimensionless acceleration σ) of a rigid plate, inclined at an angle α ∈ (0, π/2) to the exterior horizontal, as it advances (σ > 0) or retreats (σ < 0) from an initially stationary and horizontal strip of inviscid, incompressible fluid under gravity, are studied in the small-time limit via the method of matched asymptotic expansions. This work generalises the case of a uniformly accelerating plate advancing into a fluid as studied in Needham et al. (2008). Particular attention is paid to the innermost asymptotic regions encompassing the initial interaction between the plate and the free surface. We find that the structure of the solution to the governing initial boundary value problem is characterised in terms of the parameters α and μ (where μ = 1+σ tan α), with a bifurcation in structure as μ changes sign. This bifurcation in structure leads us to question the well-posedness and stability of the governing initial boundary value problem with respect to small perturbations in initial data in the innermost asymptotic regions, the discussion of which will be presented in the companion paper Gallagher et al. (2016) . In particular, when (α, μ) ∈ (0, π/2) × R+, the free surface close to the initial contact point remains monotone, and encompasses a swelling jet when (α, μ) ∈ (0, π/2)×[1,∞), or a collapsing jet when (α, μ) ∈ (0, π/2) × (0, 1). However, when (α, μ) ∈ (0, π/2) × R−, the collapsing jet develops a more complex structure, with the free surface close to the initial contact point now developing a finite number of local oscillations, with near resonance type behaviour occurring close to a countable set of critical plate angles α = α∗n ∈ (0, π/2) (n = 1, 2, . . .)
The evolution problem for the 1D nonlocal Fisher-KPP equation with a top hat kernel. Part 1. The Cauchy problem on the real line
We study the Cauchy problem on the real line for the nonlocal Fisher-KPP
equation in one spatial dimension, where
is a spatial convolution with the top hat kernel, .
After showing that the problem is globally well-posed, we demonstrate that
positive, spatially-periodic solutions bifurcate from the spatially-uniform
steady state solution as the diffusivity, , decreases through
. We explicitly construct these spatially-periodic
solutions as uniformly-valid asymptotic approximations for , over one
wavelength, via the method of matched asymptotic expansions. These consist, at
leading order, of regularly-spaced, compactly-supported regions with width of
where , separated by regions where is exponentially small at
leading order as .
From numerical solutions, we find that for , permanent form
travelling waves, with minimum wavespeed, , are generated, whilst
for , the wavefronts generated separate the regions where
from a region where a steady periodic solution is created. The structure
of these transitional travelling waves is examined in some detail
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