A computational method for the coupled solution of reaction–diffusion equations on evolving domains and manifolds: application to a model of cell migration and chemotaxis

In this paper, we devise a moving mesh finite element method for the approximate solution of coupled bulk–surface reaction–diffusion equations on an evolving two dimensional domain. Fundamental to the success of the method is the robust generation of bulk and surface meshes. For this purpose, we use a novel moving mesh partial differential equation (MMPDE) approach. The developed method is applied to model problems with known analytical solutions; these experiments indicate second-order spatial and temporal accuracy. Coupled bulk–surface problems occur frequently in many areas; in particular, in the modelling of eukaryotic cell migration and chemotaxis. We apply the method to a model of the two-way interaction of a migrating cell in a chemotactic field, where the bulk region corresponds to the extracellular region and the surface to the cell membrane

A point mass in an isotropic universe: III. The region R≤2mR\leq 2m

McVittie's solution of Einstein's field equations, representing a point mass embedded into an isotropic universe, possesses a scalar curvature singularity at proper radius $R=2m$. The singularity is space-like and precedes, in the expanding case, all other events in the space-time. It is shown here that this singularity is gravitationally weak, and the possible structure of the region $R\leq 2m$ is investigated. A characterization of this solution which does not involve asymptotics is given.Comment: Revtex, 11pp. To appear in Class.Quant.Grav. Paper II appeared as Class. Quant. Grav. 16 (1999) 122

Radial versus femoral access for rotational atherectomy: A UK observational study of 8622 patients

Background—Rotational atherectomy (RA) is an important interventional tool for heavily calcified coronary lesions. We compared the early clinical outcomes in patients undergoing RA using radial or femoral access. Methods and Results—We identified all patients in England and Wales who underwent RA between January 1, 2005, and March 31, 2014. Eight thousand six hundred twenty-two RA cases (3069 radial and 5553 femoral) were included in the analysis. The study primary outcome was 30-day mortality. Propensity scores were calculated to determine the factors associated with treatment assignment to radial or femoral access. Multivariable logistic regression analysis, using the calculated propensity scores, was performed. Thirty-day mortality was 2.2% in the radial and 2.3% in the femoral group (P=0.76). Radial access was associated with equivalent 30-day mortality (adjusted odds ratio [OR], 1.06; 95% confidence interval [CI], 0.77–1.46; P=0.71), procedural success (OR, 1.04; 95% CI, 0.84–1.29; P=0.73), major adverse cardiac and cerebrovascular events (OR, 1.05; 95% CI, 0.80–1.38; P=0.72), and net adverse clinical events (OR, 0.90; 95% CI, 0.71–1.15; P=0.41), but lower rates of in-hospital major bleeding (OR, 0.62; 95% CI, 0.40–0.98; P=0.04) and major access site complications (OR, 0.05; 95% CI, 0.01–0.38; P=0.004), compared with femoral access. Conclusions—In this large real-world study of patients undergoing RA, radial access was associated with equivalent 30-day mortality and procedural success, but reduced major bleeding and access site complications, compared with femoral access

Evidence against the Detectability of a Hippocampal Place Code Using Functional Magnetic Resonance Imaging

Individual hippocampal neurons selectively increase their firing rates in specific spatial locations. As a population, these neurons provide a decodable representation of space that is robust against changes to sensory- and path-related cues. This neural code is sparse and distributed, theoretically rendering it undetectable with population recording methods such as functional magnetic resonance imaging (fMRI). Existing studies nonetheless report decoding spatial codes in the human hippocampus using such techniques. Here we present results from a virtual navigation experiment in humans in which we eliminated visual- and path-related confounds and statistical limitations present in existing studies, ensuring that any positive decoding results would represent a voxel-place code. Consistent with theoretical arguments derived from electrophysiological data and contrary to existing fMRI studies, our results show that although participants were fully oriented during the navigation task, there was no statistical evidence for a place code

STRUCTURAL ANALYSIS AND INTERPRETATION OF DEFORMATION ALONG THE KEWEENAW FAULT SYSTEM FROM LAKE LINDEN TO MOHAWK, MICHIGAN

The Keweenaw fault is likely the most significant and most studied fault associated with the Midcontinent Rift System. The fault roughly bisects the Keweenaw Peninsula and places Portage Lake Volcanics (~1.1 Ga) over much younger Jacobsville Sandstone (~1.0 Ga). Published bedrock geology maps with cross sections from the 1950s show the fault as a single continuous trace that is locally associated with smaller cross faults and splays. The accompanying cross-sections show hanging-wall volcanic strata having a well-defined, listric geometry with dip decreasing away from the fault to the northwest. This M.S. thesis presents a structural analysis and interpretation of the Keweenaw fault system between Lake Linden and Mohawk, MI, which includes the well-known localities of Houghton-Douglass Falls, the St. Louis ravine, the Natural Wall ravine, and the anomalous rhyolite body near Copper City. Objectives of the study were to better define the geometry, movement, and slip kinematics of the Keweenaw fault while also characterizing the fold patterns associated with the fault system. Field observations and data were used to revise existing bedrock geology maps, construct new cross-sections, and analyze fold geometry and fault slip behavior to infer aspects of the tectonic regime that caused the deformation. New field mapping has refined the trace geometry of the Keweenaw fault and smaller associated faults, revised intersections between several splay faults and the main fault, and suggested the existence of several footwall splays not previously recognized. These map changes better define the Keweenaw fault system in this area as consisting of: 1) major NNE-trending segments that define the fault system’s overall trend and probably have mostly reverse slip; 2) NE-trending segments that branch off the major fault segments and define wedge-shaped fault blocks that widen to the northeast in the footwall; and 3) NNW-trending segments that connect faults of the first two types. At a point southwest of Copper City, the main fault surface abruptly changes strike from N16°E to N58°E traveling in a northeasterly direction and it shifts ~650 m deeper stratigraphically within the Portage Lake Volcanics. This abrupt change in trend and stratigraphic level of the main fault occurs at a complex junction of the Allouez Gap fault with two major segments of the Keweenaw fault at the northeast end of the Mayflower fault block. Orientation analysis of Jacobsville Sandstone strata in the footwall of the fault system defines fold axes subparallel to nearby faults and with plunge directions that change from southwest to northeast moving in the same direction. Fault-slip analysis reveals both strike slip and dip slip along the fault system rather than only reverse movement as in the generally accepted model. Measured slip directions collectively define a 0.84:1 ratio of strike-to-dip slip for the fault system, and a fault-slip inversion analysis computes a nearly north-south maximum shortening direction of 2°-182°. Fold axis trends in the current area indicate shortening along an ESE-trending line, whereas fault-slip inversion analysis indicates a north-south shortening direction

A Comparison of the Scott-Foresman Measured Reading Achievement of the Three High and Low Socioeconomic Elementary Schools in Vancouver, Washington

The problem in this investigation was to determine the influences of the high and low socioeconomic backgrounds upon reading achievement in the Vancouver (Washington) Public Elementary Schools. The investigator wanted to determine if the generally accepted premise that the higher socioeconomic level student\u27s reading achievement is greater than that of the lower socioeconomic student would be substantiated in the specific area of Vancouver, Washington

The Crackle of Contemporaneity

There comes a time to move beyond asking the broad question “What is contemporaneity?” to consider more acute ways in which this question can be traced and signalled. We consider the notion of signal to be particularly appropriate in the consideration of contemporaneity, since signals are a constitutive element of contemporary infrastructures and our experience of time even if they are relatively undetectable. They operate underneath human perceptual thresholds as carriers, controllers, and codes, while also surfacing into perceptual and semiotic registers, as signs across various media—textual, visual, and, of course, sonic—all the while accessible as traces. Perhaps in this way it is possible to experience contemporaneity at a range of different scales— from the microtemporal to the planetary—to register both our closeness and distance from it (Agamben 2009), and to exemplify how times come together disjunctively in the present

Expansion-induced contribution to the precession of binary orbits

We point out the existence of new effects of global spacetime expansion on local binary systems. In addition to a possible change of orbital size, there is a contribution to the precession of elliptic orbits, to be added to the well-known general relativistic effect in static spacetimes, and the eccentricity can change. Our model calculations are done using geodesics in a McVittie metric, representing a localized system in an asymptotically Robertson-Walker spacetime; we give a few numerical estimates for that case, and indicate ways in which the model should be improved.Comment: revtex, 7 pages, no figures; revised for publication in Classical and Quantum Gravity, with minor changes in response to referees' comment

Detection of Contact Binaries Using Sparse High Phase Angle Lightcurves

We show that candidate contact binary asteroids can be efficiently identified from sparsely sampled photometry taken at phase angles >60deg. At high phase angle, close/contact binary systems produce distinctive lightcurves that spend most of the time at maximum or minimum (typically >1mag apart) brightness with relatively fast transitions between the two. This means that a few (~5) sparse observations will suffice to measure the large range of variation and identify candidate contact binary systems. This finding can be used in the context of all-sky surveys to constrain the fraction of contact binary near-Earth objects. High phase angle lightcurve data can also reveal the absolute sense of the spin.Comment: 4 pages, 4 figures, 1 table. Accepted for publication in ApJ