Influence of adaptive mesh refinement and the hydro solver on shear-induced mass stripping in a minor-merger scenario

We compare two different codes for simulations of cosmological structure formation to investigate the sensitivity of hydrodynamical instabilities to numerics, in particular, the hydro solver and the application of adaptive mesh refinement (AMR). As a simple test problem, we consider an initially spherical gas cloud in a wind, which is an idealized model for the merger of a subcluster or galaxy with a big cluster. Based on an entropy criterion, we calculate the mass stripping from the subcluster as a function of time. Moreover, the turbulent velocity field is analyzed with a multi-scale filtering technique. We find remarkable differences between the commonly used PPM solver with directional splitting in the Enzo code and an unsplit variant of PPM in the Nyx code, which demonstrates that different codes can converge to systematically different solutions even when using uniform grids. For the test case of an unbound cloud, AMR simulations reproduce uniform-grid results for the mass stripping quite well, although the flow realizations can differ substantially. If the cloud is bound by a static gravitational potential, however, we find strong sensitivity to spurious fluctuations which are induced at the cutoff radius of the potential and amplified by the bow shock. This gives rise to substantial deviations between uniform-grid and AMR runs performed with Enzo, while the mass stripping in Nyx simulations of the subcluster is nearly independent of numerical resolution and AMR. Although many factors related to numerics are involved, our study indicates that unsplit solvers with advanced flux limiters help to reduce grid effects and to keep numerical noise under control, which is important for hydrodynamical instabilities and turbulent flows.Comment: 23 pages, 18 figures, accepted for publication by Astronomy and Computin

Localized electron state in a T-shaped confinement potential

We consider a simple model of an electron moving in a T-shaped confinement potential. This model allows for an analytical solution that explicitly demonstrates the existence of laterally bound electron states in quantum wires obtained by the cleaved edge overgrowth technique.Comment: 6 pages, 5 figure

Communication interventions in adult and pediatric oncology: A scoping review and analysis of behavioral targets

BackgroundImproving communication requires that clinicians and patients change their behaviors. Interventions might be more successful if they incorporate principles from behavioral change theories. We aimed to determine which behavioral domains are targeted by communication interventions in oncology.MethodsSystematic search of literature indexed in Ovid Medline, Embase, Scopus, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Clinicaltrials.gov (2000-October 2018) for intervention studies targeting communication behaviors of clinicians and/or patients in oncology. Two authors extracted the following information: population, number of participants, country, number of sites, intervention target, type and context, study design. All included studies were coded based on which behavioral domains were targeted, as defined by Theoretical Domains Framework.FindingsEighty-eight studies met inclusion criteria. Interventions varied widely in which behavioral domains were engaged. Knowledge and skills were engaged most frequently (85%, 75/88 and 73%, 64/88, respectively). Fewer than 5% of studies engaged social influences (3%, 3/88) or environmental context/resources (5%, 4/88). No studies engaged reinforcement. Overall, 7/12 behavioral domains were engaged by fewer than 30% of included studies. We identified methodological concerns in many studies. These 88 studies reported 188 different outcome measures, of which 156 measures were reported by individual studies.ConclusionsMost communication interventions target few behavioral domains. Increased engagement of behavioral domains in future studies could support communication needs in feasible, specific, and sustainable ways. This study is limited by only including interventions that directly facilitated communication interactions, which excluded stand-alone educational interventions and decision-aids. Also, we applied stringent coding criteria to allow for reproducible, consistent coding, potentially leading to underrepresentation of behavioral domains

Twentieth Annual Convention of the College Theology Society

News release announces that the twentieth annual convention of the College Theology Society will be held at the University of Dayton

Premise Selection and External Provers for HOL4

Learning-assisted automated reasoning has recently gained popularity among the users of Isabelle/HOL, HOL Light, and Mizar. In this paper, we present an add-on to the HOL4 proof assistant and an adaptation of the HOLyHammer system that provides machine learning-based premise selection and automated reasoning also for HOL4. We efficiently record the HOL4 dependencies and extract features from the theorem statements, which form a basis for premise selection. HOLyHammer transforms the HOL4 statements in the various TPTP-ATP proof formats, which are then processed by the ATPs. We discuss the different evaluation settings: ATPs, accessible lemmas, and premise numbers. We measure the performance of HOLyHammer on the HOL4 standard library. The results are combined accordingly and compared with the HOL Light experiments, showing a comparably high quality of predictions. The system directly benefits HOL4 users by automatically finding proofs dependencies that can be reconstructed by Metis

Early stage of crystallization of (Zr1-xHfx)62Ni38 metallic glasses

This paper reports a directly observable correlation between the chemical short-range order and the electrical resistivity in metallic glasses. The phase transition corresponding to the first exotherm observed in a differential-scanning-calorimetry (DSC) scan on (Zr1-xHfx)62Ni38 is peculiar in a sense that, contrary to usual metallic glasses, this transition is associated with an increase in electrical resistivity, and x-ray diffraction measurements taken just after the DSC peak shows only the broad diffuse band characteristic of the glassy phase. Electrical resistivity, differential scanning calorimetry, low-temperature superconducting measurements, high-angle x-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy are used to study this transition in detail

Electrical resistivity and structural changes upon relaxation and crystallisation of (Mo_(0.6)Ru_(0.4))_(100-x)B_x metallic glasses

Crystallisation of (Mo_(0.6)Ru_(0.4))100_(-x)B_x glasses takes place in three steps: the first step corresponds to the precipitation of the sigma phase Mo_5Ru_3 which decomposes at higher temperatures, the second step is associated with the formation of an HCP solid solution of Mo in Ru, and in the last step the remaining amorphous matrix crystallises in an FCC boride. Detailed electrical resistivity measurements taken below the crystallisation temperature reveal an excess resistivity above the usual linear temperature dependence predicted by the Ziman theory. The increase in resistivity is associated with the onset of long-range compositional inhomogeneity (spinodal decomposition) and the decrease with the onset of crystallisation. The electrical behaviour for samples pre-annealed for 12 hours at various temperatures suggests that boron migration is partly responsible for this excess resistivity. The changes in the radial distribution function of (Mo_(0.6)Ru_(0.4))_(78)B_(22) during annealing at 525 ºC are also reported. The Mott s-d scattering model does not seem to be applicable to these amorphous alloys. The data suggest instead that an important contribution to the conduction comes from the d electrons