DSC-34291 SIMULATING DISTRIBUTED-PARAMETER MULTIPHASE THERMODYNAMIC SYSTEMS USING BOND GRAPHS

ABSTRACT The use of convection bond graphs with temperature, mass and volume as state variables allows the associated thermodynamic properties of a wide variety of single and multi-phase fluids to be found accurately without iteration, using available formulas. As a result, non-experts can simulate efficiently unsteady systems with compressible flow and heat transfer, as long as the system is modeled with discrete compartments. This paper addresses the discretization of a heat exchanger under changing phase conditions into a finite element model, assuming no slip between phases in thermodynamic equilibrium and neglecting coherent kinetic energy. The staggered grid approach used in conventional numerical analyses for flowing systems is accommodated naturally. Partial upwinding is used to control numerically induced oscillations. The wall shear and the heat transfer are keyed to standard models for laminar and turbulent flow in single-phase and two-phase regimes. A condenser of a refrigeration cycle is given to illustrate the procedure and its results

Non-existence of Skyrmion-Skyrmion and Skyrmion-anti-Skyrmion static equilibria

We consider classical static Skyrmion-anti-Skyrmion and Skyrmion-Skyrmion configurations, symmetric with respect to a reflection plane, or symmetric up to a $G$-parity transformation respectively. We show that the stress tensor component completely normal to the reflection plane, and hence its integral over the plane, is negative definite or positive definite respectively. Classical Skyrmions always repel classical Skyrmions and classical Skyrmions always attract classical anti-Skyrmions and thus no static equilibrium, whether stable or unstable, is possible in either case. No other symmetry assumption is made and so our results also apply to multi-Skyrmion configurations. Our results are consistent with existing analyses of Skyrmion forces at large separation, and with numerical results on Skymion-anti-Skyrmion configurations in the literature which admit a different reflection symmetry. They also hold for the massive Skyrme model. We also point out that reflection symmetric self-gravitating Skyrmions or black holes with Skyrmion hair cannot rest in symmetric equilibrium with self-gravitating anti-Skyrmions.Comment: v2 Typos corrected, refs added. v3 Journal versio

A Systematic Examination of Particle Motion in a Collapsing Magnetic Trap Model for Solar Flares

Context. It has been suggested that collapsing magnetic traps may contribute to accelerating particles to high energies during solar flares. Aims. We present a detailed investigation of the energization processes of particles in collapsing magnetic traps, using a specific model. We also compare for the first time the energization processes in a symmetric and an asymmetric trap model. Methods. Particle orbits are calculated using guiding centre theory. We systematically investigate the dependence of the energization process on initial position, initial energy and initial pitch angle. Results. We find that in our symmetric trap model particles can gain up to about 50 times their initial energy, but that for most initial conditions the energy gain is more moderate. Particles with an initial position in the weak field region of the collapsing trap and with pitch angles around 90 degrees achieve the highest energy gain, with betatron acceleration of the perpendicular energy the dominant energization mechanism. For particles with smaller initial pitch angle, but still outside the loss cone, we find the possibility of a significant increase in parallel energy. This increase in parallel energy can be attributed to the curvature term in the parallel equation of motion and the associated energy gain happens in the center of the trap where the field line curvature has its maximum. We find qualitatively similar results for the asymmetric trap model, but with smaller energy gains and a larger number of particles escaping from the trap.Comment: 11 pages, 13 figures. To be published in Astronomy and Astrophysic

Reconstructing the 3-D Trajectories of CMEs in the Inner Heliosphere

A method for the full three-dimensional (3-D) reconstruction of the trajectories of coronal mass ejections (CMEs) using Solar TErrestrial RElations Observatory (STEREO) data is presented. Four CMEs that were simultaneously observed by the inner and outer coronagraphs (COR1 and 2) of the Ahead and Behind STEREO satellites were analysed. These observations were used to derive CME trajectories in 3-D out to ~15Rsun. The reconstructions using COR1/2 data support a radial propagation model. Assuming pseudo-radial propagation at large distances from the Sun (15-240Rsun), the CME positions were extrapolated into the Heliospheric Imager (HI) field-of-view. We estimated the CME velocities in the different fields-of-view. It was found that CMEs slower than the solar wind were accelerated, while CMEs faster than the solar wind were decelerated, with both tending to the solar wind velocity.Comment: 17 pages, 10 figures, 1 appendi

Experiences of UK and Irish family carers of people with profound and multiple intellectual disabilities during the COVID-19 pandemic

Background: People with profound and multiple intellectual disabilities (PMID) have high and intensive support needs that ordinarily place significant strain on family carers. This was further heightened by the removal of many external supports during the COVID-19 pandemic. We sought to explore the experiences of family carers of people with PMID during the COVID-19 pandemic and understand what the longer-term impact might be on their lives. Methods: Focus group interviews (n = 32) were conducted with family carers (n = 126) from the four countries of the UK and the Republic of Ireland. Participants were asked questions relating to their experiences of the COVID-19 pandemic, coping strategies, and challenges faced. All focus groups were conducted using the online platform, Zoom. These were audio recorded, transcribed verbatim and analysed employing inductive thematic analysis. Findings: Three main themes were generated from the data including (1.0) COVID-19 as a double-edged sword (2.0), The struggle for support (3.0), Constant nature of caring. These included 11 subthemes. (1.1) ‘COVID-19 as a catalyst for change’, (1.2) ‘Challenges during COVID-19: dealing with change’, (1.3) ‘Challenges during COVID-19: fear of COVID-19’, (1.4); ‘The online environment: the new normal’ (2.1) ‘Invisibility of male carers’, (2.2) ‘Carers supporting carers’, (2.3) ‘The only service you get is lip service: non-existent services’, (2.4); ‘Knowing your rights’ (3.1) ‘Emotional response to the caring role: Feeling devalued’, (3.2) ‘Emotional response to the caring role: Desperation of caring’, (3.3) ‘Multiple demands of the caring role.’ Conclusions: The COVID-19 pandemic presented immense challenges to family carers of people with PMID but also provided some opportunities. Families had already struggled to receive many of the supports and services to which they were entitled to only to have these removed at the onset of the pandemic. The experiences of male carers have been largely absent from the literature with this research showing they want to be included in decision making and require tailored support services. Service providers should see the end of the COVID-19 pandemic as providing opportunity to re-examine current provision and design services with family carers. As the direct threat from COVID-19 diminishes and the experiences of those who lived through this period come to the fore, there is a need to re-examine current models and provision of support to family carers to better meet their needs

XMM-Newton and Chandra observations of three X-ray faint early-type galaxies

We present XMM-Newton observations of three X-ray under-luminous elliptical galaxies, NGC 3585, NGC 4494 and NGC 5322. All three galaxies have relatively large optical luminosities (log LB=10.35-10.67 solar) but have X-ray luminosities consistent with emission from discrete sources only. In conjunction with a Chandra observation of NGC 3585, we analyse the XMM data and show that the three galaxies are dominated by discrete source emission, but do possess some X-ray emitting gas. The gas is at relatively low temperatures, kT=0.25-0.44 keV. All three galaxies show evidence of recent dynamical disturbance and formation through mergers, including kinematically distinct cores, young stellar ages, and embedded stellar disks. This leads us to conclude that the galaxies formed relatively recently and have yet to build up large X-ray halos. They are likely to be in a developmental phase where the X-ray gas has a very low density, making it undetectable outside the galaxy core. However, if the gas is a product of stellar mass loss, as seems most probable, we would expect to observe supersolar metal abundances. While abundance is not well constrained by the data, we find best fit abundances <0.1 solar for single-temperature models, and it seems unlikely that we could underestimate the metallicity by such a large factor.Comment: Accepted for publication in MNRAS, 12 pages, 8 postscript figure

New Light on the Formation and Evolution of M31 and its Globular Cluster System

We present spectroscopic ages, metallicities, and [alpha/Fe] ratios for 70 globular clusters in M31 that were derived from Lick line-index measurements. In addition to a population of old (>10 Gyr) globular clusters with a wide range of metallicities, from about -2.0 dex to solar values, we find evidence for a population of intermediate-age globular clusters with ages between ~5 and 8 Gyr and a mean metallicity around [Z/H]=-0.6. We also confirm the presence of young M31 globular clusters that were recently identified by Beasley et al. (2004), which have ages <1 Gyr and relatively high metallicities around -0.4 dex. The M31 globular cluster system has a clearly super-solar mean [alpha/Fe]=0.14\pm0.04 dex. Intermediate-age and young objects show roughly solar abundance ratios. We find evidence for an age-[alpha/Fe] relation in the sense that younger clusters have smaller mean [alpha/Fe] ratios. From a comparison of indices, mostly sensitive to carbon and/or nitrogen abundance, with SSP model predictions for nitrogen-enhanced stellar populations, we find a dichotomy in nitrogen enhancement between young and old M31 globular clusters. The indices of objects older than 5 Gyr are consistent with a factor of three or higher in nitrogen enhancement compared to their younger counterparts. Using kinematical data from Morrison et al. (2004) we find that the globular cluster sub-population with halo kinematics is old (>9 Gyr), has a bimodal metallicity distribution, and super-solar [alpha/Fe]. Disk globular clusters have a wider range of ages, are on average more metal-rich, and have a slightly smaller mean [alpha/Fe] ratio. (abridged)Comment: 32 pages, 12 figures, accepted for publication in A&

Idelalisib sensitivity and mechanisms of disease progression in relapsed TCF3-PBX1 acute lymphoblastic leukemia

Peer reviewe

Exogenous 17-β estradiol administration blunts progression of established angiotensin II-induced abdominal aortic aneurysms in female ovariectomized mice

BACKGROUND: Abdominal aortic aneurysms (AAAs) occur predominately in males. However, AAAs in females have rapid growth rates and rupture at smaller sizes. Mechanisms contributing to AAA progression in females are undefined. We defined effects of ovariectomy, with and without 17-β estradiol (E2), on progression of established angiotensin II (AngII)-induced AAAs in female mice. METHODS: We used neonatal testosterone exposures at 1 day of age to promote susceptibility to AngII-induced AAAs in adult female Ldlr(−/−) mice. Females were infused with AngII for 28 days to induce AAAs, and then stratified into groups that were sham, ovariectomized (Ovx, vehicle), or Ovx with E2 administration for 2 months of continued AngII infusions. Aortic lumen diameters were quantified by ultrasound and analyzed by linear mixed model, and maximal AAA diameters were analyzed by one-way ANOVA. Atherosclerosis was quantified en face in the aortic arch. AAA tissue sections were analyzed for cellular composition. We quantified effects of E2 on abdominal aortic smooth muscle cell (SMC) growth, α-actin and transforming growth factor-beta (TGF-β) production, and wound healing. RESULTS: Serum E2 concentrations were increased significantly by E2. Aortic lumen diameters increased over time in sham-operated and Ovx (vehicle) females, but not in Ovx females administered E2. At day 70, E2 administration decreased significantly aortic lumen diameters compared to Ovx vehicle and sham-operated females. Compared to Ovx females (vehicle), maximal AAA diameters were reduced significantly by E2. AAA tissue sections from Ovx females administered E2 exhibited significant increases in α-actin and decreases in neutrophils compared to Ovx females administered vehicle. In abdominal aortic SMCs, E2 resulted in a concentration-dependent increase in α-actin, elevated TGF-β, and more rapid wound healing. E2 administration to Ovx females also significantly reduced atherosclerotic lesions compared to sham-operated females. This effect was accompanied by significant reductions in serum cholesterol concentrations. CONCLUSIONS: E2 administration to Ovx females abolished progressive growth and decreased severity of AngII-induced AAAs. These effects were accompanied by increased SMC α-actin, elevated TGF-β, and reduced neutrophils. Similarly, E2 administration reduced AngII-induced atherosclerosis. These results suggest that loss of E2 in post-menopausal females may contribute to progressive growth of AAAs. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13293-015-0030-1) contains supplementary material, which is available to authorized users