Locating a blockage in the cerebral vascular network

Ischemic strokes make up 70-80% of strokes, and are characterised by blockages of arteries carrying blood to the brain. This problem involves the identification of blockages using a species distribution derived from an MRI scan of the brain. Blood flow in the brain may be described using a network of branching vessels which are the sources for porous media-type flow in the capillary bed. The topologically intricate nature of the branching blood vessels hinder most attempts at simplifying the problem, and the report concludes that a longer-term modelling process would be required in order to provide therapeutically useful conclusions. Some recommendations for the direction such future work could take are also included

An estimate of energy dissipation due to soil-moisture hysteresis

Processes of infiltration, transport and outflow in unsaturated soil necessarily involve the dissipation of energy through various processes. Accounting for these energetic processes can contribute to modelling hydrological and ecological systems. The well-documented hysteretic relationship between matric potential and moisture content in soil suggests that one such mechanism of energy dissipation is associated with the cycling between wetting and drying processes. Working from a time-series of soil moisture content data (taken in the south-west of Ireland), and making rather straightforward assumptions regarding the hysteretic relationship mentioned, the average rate of energy dissipation was found to be O(10−5)

A locally adaptive time-stepping algorithm for\ud petroleum reservoir simulations

An algorithm for locally adapting the step-size for large scale finite volume simulations of multi-phase flow in petroleum reservoirs is suggested which allows for an “all-in-one” implicit calculation of behaviour over a very large time scale. Some numerical results for simple two-phase flow in one space dimension illustrate the promise of the algorithm, which has also been applied to very simple 3D cases. A description of the algorithm is presented here along with early results. Further development of the technique is hoped to facilitate useful scaling properties

Hysteresis and Post Walrasian Economics

Macroeconomics, hysteresis The “new consensus” dsge (dynamic stochastic general equilibrium) macroeconomic model has microfoundations provided by a single representative agent. In this model shocks to the economic environment do not have any lasting effects. In reality adjustments at the micro level are made by heterogeneous agents, and the aggregation problem cannot be assumed away. In this paper we show that the discontinuous adjustments made by heterogeneous agents at the micro level mean that shocks have lasting effects, aggregate variables containing a selective, erasable memory of the shocks experienced. This hysteresis framework provides foundations for the post-Walrasian analysis of macroeconomic systems

Homogeneous cooling of rough, dissipative particles: Theory and simulations

We investigate freely cooling systems of rough spheres in two and three dimensions. Simulations using an event driven algorithm are compared with results of an approximate kinetic theory, based on the assumption of a generalized homogeneous cooling state. For short times $t$, translational and rotational energy are found to change linearly with $t$. For large times both energies decay like $t^{-2}$ with a ratio independent of time, but not corresponding to equipartition. Good agreement is found between theory and simulations, as long as no clustering instability is observed. System parameters, i.e. density, particle size, and particle mass can be absorbed in a rescaled time, so that the decay of translational and rotational energy is solely determined by normal restitution and surface roughness.Comment: 10 pages, 10 eps-figure

Fostering Sustainability in Higher Education: A Mixed-Methods Study of Transformative Leadership and Change Strategies

As evidence of the earth’s limited capacity to sustain human life mounts, institutions of higher education are being looked to for leadership in the effort to educate students about environmental concerns and support the development of sustainable innovations. Colleges and universities are responding to this call for leadership by starting and/or expanding environmental research programs, integrating sustainability issues throughout the curriculum, adopting sustainable operations, and building green facilities. Reflecting upon the sustainability efforts of these institutions, this research study explores the following questions: What factors are essential for initiating and leading a successful change effort to foster sustainability in higher education? What processes guide higher education institutions in efforts to deeply and comprehensively implement sustainable changes? A sequential mixed-methods research design was used to gather data from questionnaires administered to 86 colleges and universities in the United States implementing sustainability programs, from interviews with 20 individuals who are guiding the change processes at ten different institutions, and from archival records documenting the initiatives and outcomes at these colleges and universities. After the data had been analyzed to identify common themes, factors and change process strategies, the results of the analyses were examined in relationship to existing models of change in higher education. Significant correlations were found between the change strategies used and the support systems provided by these institutions and the level of progress achieved on the sustainability initiatives. The electronic version of this dissertation is accessible at the OhioLINK ETD Center, https://etd.ohiolink.edu

Fostering Sustainability in Higher Education: A Mixed-Methods Study of Transformative Leadership and Change Strategies

As evidence of the earth’s limited capacity to sustain human life mounts, institutions of higher education are being looked to for leadership in the effort to educate students about environmental concerns and support the development of sustainable innovations. Colleges and universities are responding to this call for leadership by starting and/or expanding environmental research programs, integrating sustainability issues throughout the curriculum, adopting sustainable operations, and building green facilities. Reflecting upon the sustainability efforts of these institutions, this research study explores the following questions: What factors are essential for initiating and leading a successful change effort to foster sustainability in higher education? What processes guide higher education institutions in efforts to deeply and comprehensively implement sustainable changes? A sequential mixed-methods research design was used to gather data from questionnaires administered to 86 colleges and universities in the United States implementing sustainability programs, from interviews with 20 individuals who are guiding the change processes at ten different institutions, and from archival records documenting the initiatives and outcomes at these colleges and universities. After the data had been analyzed to identify common themes, factors and change process strategies, the results of the analyses were examined in relationship to existing models of change in higher education. Significant correlations were found between the change strategies used and the support systems provided by these institutions and the level of progress achieved on the sustainability initiatives. The electronic version of this dissertation is accessible at the OhioLINK ETD Center, https://etd.ohiolink.edu

Time-Series Ensemble Photometry and the Search for Variable Stars in the Open Cluster M11

This work presents the first large-scale photometric variability survey of the intermediate age (~200 Myr) open cluster M11. Thirteen nights of data over two observing seasons were analyzed (using crowded field and ensemble photometry techniques) to obtain high relative precision photometry. In this study we focus on the detection of candidate member variable stars for follow-up studies. A total of 39 variable stars were detected and can be categorized as follows: 1 irregular (probably pulsating) variable, 6 delta Scuti variables, 14 detached eclipsing binary systems, 17 W UMa variables, and 1 unidentified/candidate variable. While previous proper motion studies allow for cluster membership determination for the brightest stars, we find that membership determination is significantly hampered below V=15,R=15.5 by the large population of field stars overlapping the cluster MS. Of the brightest detected variables that have a high likelihood of cluster membership, we find five systems where further work could help constrain theoretical stellar models, including one potential W UMa member of this young cluster.Comment: 38 pages, 13 figures, accepted for December 2005 AJ, high-resolution version available upon reques

Inside the Bondi radius of M87

Chandra X-ray observations of the nearby brightest cluster galaxy M87 resolve the hot gas structure across the Bondi accretion radius of the central supermassive black hole, a measurement possible in only a handful of systems but complicated by the bright nucleus and jet emission. By stacking only short frame-time observations to limit pileup, and after subtracting the nuclear PSF, we analysed the X-ray gas properties within the Bondi radius at 0.12-0.22 kpc (1.5-2.8 arcsec), depending on the black hole mass. Within 2 kpc radius, we detect two significant temperature components, which are consistent with constant values of 2 keV and 0.9 keV down to 0.15 kpc radius. No evidence was found for the expected temperature increase within ~0.25 kpc due to the influence of the SMBH. Within the Bondi radius, the density profile is consistent with $\rho\propto r^{-1}$. The lack of a temperature increase inside the Bondi radius suggests that the hot gas structure is not dictated by the SMBH's potential and, together with the shallow density profile, shows that the classical Bondi rate may not reflect the accretion rate onto the SMBH. If this density profile extends in towards the SMBH, the mass accretion rate onto the SMBH could be at least two orders of magnitude less than the Bondi rate, which agrees with Faraday rotation measurements for M87. We discuss the evidence for outflow from the hot gas and the cold gas disk and for cold feedback, where gas cooling rapidly from the hot atmosphere could feed the cirumnuclear disk and fuel the SMBH. At 0.2 kpc radius, the cooler X-ray temperature component represents ~20% of the total X-ray gas mass and, by losing angular momentum to the hot gas component, could provide a fuel source of cold clouds within the Bondi radius.Comment: 14 pages, 8 figures, accepted by MNRA

"Everyone here wants everyone else to get better": the role of social identity in eating disorder recovery

Retention of a positively valued illness identity contributes to poor outcomes for individuals with eating disorders. Consequently, dis-identification from the illness identity and the adoption of a recovery identity is vital for successful recovery. While social identity processes have been shown to influence eating disorder maintenance, their role in recovery is rarely considered. This study explores how a sense of shared identity helps individuals with eating disorders manage their condition and promotes recovery. Transcripts from 18 online support sessions involving 75 participants were thematically analysed. Our findings suggest that the illness identity initially operates as a social identity that forms the basis for connections with similar others. For those wishing to recover, identity-based support is then perceived to be more effective than that found outside the group. Online interactions also facilitate construction of a new shared recovery identity which promotes a shift from the illness identity as a primary source of definition and endorses group norms of illness disclosure and treatment engagement. While in the clinical literature, eating disorder identity is seen as problematic and interventions are targeted at challenging an individual’s self-concept, we suggest that interventions could instead harness identity resources to support a transition to a recovery identity