The diffuse Nitsche method: Dirichlet constraints on phase-field boundaries

We explore diffuse formulations of Nitsche's method for consistently imposing Dirichlet boundary conditions on phase-field approximations of sharp domains. Leveraging the properties of the phase-field gradient, we derive the variational formulation of the diffuse Nitsche method by transferring all integrals associated with the Dirichlet boundary from a geometrically sharp surface format in the standard Nitsche method to a geometrically diffuse volumetric format. We also derive conditions for the stability of the discrete system and formulate a diffuse local eigenvalue problem, from which the stabilization parameter can be estimated automatically in each element. We advertise metastable phase-field solutions of the Allen-Cahn problem for transferring complex imaging data into diffuse geometric models. In particular, we discuss the use of mixed meshes, that is, an adaptively refined mesh for the phase-field in the diffuse boundary region and a uniform mesh for the representation of the physics-based solution fields. We illustrate accuracy and convergence properties of the diffuse Nitsche method and demonstrate its advantages over diffuse penalty-type methods. In the context of imaging based analysis, we show that the diffuse Nitsche method achieves the same accuracy as the standard Nitsche method with sharp surfaces, if the inherent length scales, i.e., the interface width of the phase-field, the voxel spacing and the mesh size, are properly related. We demonstrate the flexibility of the new method by analyzing stresses in a human vertebral body

A new Cambrian arthropod, Emeraldella brutoni, from Utah

Emeraldella is a rare arthropod of relatively large body size that belongs with the trilobite-like arthropods, Artiopoda. E. brutoni n. sp. from the Wheeler Formation of west-central Utah is the second species described and marks the first confirmed occurrence of Emeraldella outside the Burgess Shale of British Columbia. An articulated, flagelliform telson, similar to that of the Burgess Shale taxon Molaria, is recognized in Emeraldella. Evidence for the presence of lamellae on the exopods of Molaria is presented, supporting affinity of that taxon with Artiopoda. A close relationship between Emeraldella and Molaria is tentatively suggested, based on the morphology of tergites and telson

Traces for star products on the dual of a Lie algebra

In this paper, we describe all traces for the BCH star-product on the dual of a Lie algebra. First we show by an elementary argument that the BCH as well as the Kontsevich star-product are strongly closed if and only if the Lie algebra is unimodular. In a next step we show that the traces of the BCH star-product are given by the \ad-invariant functionals. Particular examples are the integration over coadjoint orbits. We show that for a compact Lie group and a regular orbit one can even achieve that this integration becomes a positive trace functional. In this case we explicitly describe the corresponding GNS representation. Finally we discuss how invariant deformations on a group can be used to induce deformations of spaces where the group acts on.Comment: 18 pages, LaTeX2e. Updated reference

Line formation in solar granulation: II. The photospheric Fe abundance

The solar photospheric Fe abundance has been determined using realistic ab initio 3D, time-dependent, hydrodynamical model atmospheres. The study is based on the excellent agreement between the predicted and observed line profiles directly rather than equivalent widths, since the intrinsic Doppler broadening from the convective motions and oscillations provide the necessary non-thermal broadening. Thus, three of the four hotly debated parameters (equivalent widths, microturbulence and damping enhancement factors) in the center of the recent solar Fe abundance dispute regarding Fe i lines no longer enter the analysis, leaving the transition probabilities as the main uncertainty. Both Fe i (using the samples of lines of both the Oxford and Kiel studies) and Fe ii lines have been investigated, which give consistent results: log epsilon_FeI = 7.44 +/- 0.05 and log epsilon_FeII = 7.45 +/- 0.10. Also the wings of strong Fe i lines return consistent abundances, log epsilon_FeII = 7.42 +/- 0.03, but due to the uncertainties inherent in analyses of strong lines we give this determination lower weight than the results from weak and intermediate strong lines. In view of the recent slight downward revision of the meteoritic Fe abundance log epsilon_Fe = 7.46 +/- 0.01, the agreement between the meteoritic and photospheric values is very good, thus appearingly settling the debate over the photospheric Fe abundance from Fe i lines

Nuclear structure-gene expression interrelationships: implications for aberrant gene expression in cancer

There is long-standing recognition that transformed and tumor cells exhibit striking alterations in nuclear morphology as well as in the representation and intranuclear distribution of nucleic acids and regulatory factors. Parameters of nuclear structure support cell growth and phenotypic properties of cells by facilitating the organization of genes, replication and transcription sites, chromatin remodeling complexes, transcripts, and regulatory factors in structurally and functionally definable subnuclear domains within the three-dimensional context of nuclear architecture. The emerging evidence for functional interrelationships of nuclear structure and gene expression is consistent with linkage of tumor-related modifications in nuclear organization to compromised gene regulation during the onset and progression of cancer

A modelling tool for capacity planning in acute and community stroke services

Background: Mathematical capacity planning methods that can take account of variations in patient complexity, admission rates and delayed discharges have long been available, but their implementation in complex pathways such as stroke care remains limited. Instead simple average based estimates are commonplace. These methods often substantially underestimate capacity requirements. We analyse the capacity requirements for acute and community stroke services in a pathway with over 630 admissions per year. We sought to identify current capacity bottlenecks affecting patient flow, future capacity requirements in the presence of increased admissions, the impact of co-location and pooling of the acute and rehabilitation units and the impact of patient subgroups on capacity requirements. We contrast these results to the often used method of planning by average occupancy, often with arbitrary uplifts to cater for variability. Methods: We developed a discrete-event simulation model using aggregate parameter values derived from routine administrative data on over 2000 anonymised admission and discharge timestamps. The model mimicked the flow of stroke, high risk TIA and complex neurological patients from admission to an acute ward through to community rehab and early supported discharge, and predicted the probability of admission delays. Results: An increase from 10 to 14 acute beds reduces the number of patients experiencing a delay to the acute stroke unit from 1 in every 7 to 1 in 50. Co-location of the acute and rehabilitation units and pooling eight beds out of a total bed stock of 26 reduce the number of delayed acute admissions to 1 in every 29 and the number of delayed rehabilitation admissions to 1 in every 20. Planning by average occupancy would resulted in delays for 1 in every 5 patients in the acute stroke unit. Conclusions: Planning by average occupancy fails to provide appropriate reserve capacity to manage the variations seen in stroke pathways to desired service levels. An appropriate uplift from the average cannot be based simply on occupancy figures. Our method draws on long available, intuitive, but underused mathematical techniques for capacity planning. Implementation via simulation at our study hospital provided valuable decision support for planners to assess future bed numbers and organisation of the acute and rehabilitation services. <br/

Evaluating Measures of Fidelity for Substance Abuse Group Treatment With Incarcerated Adolescents

The evaluation of treatment fidelity has become increasingly important as the demand for evidence-based practice grows. The purpose of the present study is to describe the psychometric properties of two measures of treatment fidelity that can be used by therapists and supervisors - one for group-based cognitive–behavioral therapy (CBT) and one for combined Substance Education and Twelve-Step Introduction (SET) for adolescent substance use. At the end of group sessions (CBT n = 307; SET n = 279), therapists and supervisors completed an evaluation measure assessing adherence to certain core components of the intervention. The supervisor version of the fidelity measure also included items for rating the level of competency the therapist demonstrated when providing each component of the intervention. Results from split-half cross-validation analyses provide strong support for an 11-item, three-factor CBT fidelity measure. Somewhat less consistent but adequate support for a nine-item, two-factor SET fidelity measure was found. Internal consistencies ranged from acceptable to good for both the CBT and SET adherence scales and from acceptable to good for the CBT and SET competency scales, with the exception of the CBT practices competency scale. Preliminary validation of the measures suggests that both measures have adequate to strong factor structure, reliability, and concurrent and discriminant validity. The results of this study have implications for research and clinical settings, including the supervision process

Improvements to stellar structure models, based on a grid of 3D convection simulations - I. T(t) relations

Relations between temperature, T, and optical depth, τ, are often used for describing the photospheric transition from optically thick to optically thin in stellar structure models. We show that this is well justified, but also that currently used T(τ

Flexible provisioning of Web service workflows

Web services promise to revolutionise the way computational resources and business processes are offered and invoked in open, distributed systems, such as the Internet. These services are described using machine-readable meta-data, which enables consumer applications to automatically discover and provision suitable services for their workflows at run-time. However, current approaches have typically assumed service descriptions are accurate and deterministic, and so have neglected to account for the fact that services in these open systems are inherently unreliable and uncertain. Specifically, network failures, software bugs and competition for services may regularly lead to execution delays or even service failures. To address this problem, the process of provisioning services needs to be performed in a more flexible manner than has so far been considered, in order to proactively deal with failures and to recover workflows that have partially failed. To this end, we devise and present a heuristic strategy that varies the provisioning of services according to their predicted performance. Using simulation, we then benchmark our algorithm and show that it leads to a 700% improvement in average utility, while successfully completing up to eight times as many workflows as approaches that do not consider service failures