A Phase Lag between Disk and Corona in GRMHD Simulations of Precessing Tilted Accretion Disks

In the course of its evolution, a black hole (BH) accretes gas from a wide range of directions. Given a random accretion event, the typical angular momentum of an accretion disc would be tilted by $\sim$60$^\circ$ relative to the BH spin. Misalignment causes the disc to precess at a rate that increases with BH spin and tilt angle. We present the first general-relativistic magnetohydrodynamic (GRMHD) simulations spanning a full precession period of highly tilted (60$^\circ$), moderately thin ($h/r=0.1$) accretion discs around a rapidly spinning ($a\simeq0.9$) BH. While the disc and jets precess in phase, we find that the corona, sandwiched between the two, lags behind by $\gtrsim 10^{\circ}$. For spectral models of BH accretion, the implication is that hard non-thermal (corona) emission lags behind the softer (disc) emission, thus potentially explaining some properties of the hard energy lags seen in Type-C low frequency quasi-periodic oscillations in X-Ray binaries. While strong jets are unaffected by this disc-corona lag, weak jets stall when encountering the lagging corona at distances $r \sim 100$ black hole radii. This interaction may quench large-scale jet formation.Comment: 5 pages, 4 figures, submitted to MNRAS, see YouTube playlist for 3D renderings: https://www.youtube.com/playlist?list=PLDO1oeU33GwmwOV_Hp9s7572JdU8JPSS

Developing the framework for multi-criteria assessment of smart local energy systems

In response to the climate emergency, energy landscapes are rapidly shifting to cleaner, decentralised smart local energy systems (SLESs). SLES will facilitate connection of transport, heat and power through flexible energy supply, demand and storage options supported by digital technology. SLESs are expected to contribute to tackling the energy trilemma (cost, security and sustainability), but there is also scope for them to offer many co-benefits aligned with the United Nations (UN) Sustainable Development Goals (SDGs). These benefits may drive for ongoing political and financial investment in SLES; therefore, there’s a need to indicate how a SLES is performing over time relative to each of them. Currently, there is no standardised approach to evaluate SLES and most of the existing techno-socio-economic tools have limited scope to assess the complex multiple performance indices, scenarios and stakeholders. The Innovate UK-funded EnergyREV research consortium is developing a multi-criteria assessment tool (MCA) for SLES. This paper describes the first step in this process – developing a simplified and standardised framework for assessing the performance of the system and the realization of benefits. It explores existing protocols and stakeholder opinion to identify 50 potential factors that are important in monitoring the system performance. These are clustered into 10 key themes to create a taxonomy for SLES performance that are aligned with relevant UN SDGs to track wider co-benefits. The resulting MCA tool will be instrumental to project stakeholders in providing evidence to support performance claims and identifying potential benefits beyond targeted key performance indicators

Penetration of human skin by the cercariae of Schistosoma mansoni : an investigation of the effect of multiple cercarial applications

It has previously been postulated that L-arginine emitted by penetrating Schistosoma mansoni cercariae serves as an intraspecific signal guiding other cercariae to the penetration site. It was suggested that penetrating in groups offers a selective advantage. If this hypothesis is correct and group penetration at one site on the host offers an advantage, it would follow that at such a site, successive groups of cercariae would be able to penetrate skin in either greater numbers or at a faster rate. This prediction was tested by the use of an in vitro model of cercarial penetration based on the Franz cell and using human skin. It was demonstrated that there was no increase in the percentage of cercariae able to penetrate the skin with subsequent exposures. Consequently, it seems unlikely that the release of L-arginine by cercariae during penetration could have evolved as a specific orientation system based on a selective advantage offered by group penetration.Peer reviewe

Internal Friction and Vulnerability of Mixed Alkali Glasses

Based on a hopping model we show how the mixed alkali effect in glasses can be understood if only a small fraction c_V ofthe available sites for the mobile ions is vacant. In particular, we reproduce the peculiar behavior of the internal friction and the steep fall (''vulnerability'') of the mobility of the majority ion upon small replacements by the minority ion. The single and mixed alkali internal friction peaks are caused by ion-vacancy and ion-ion exchange processes. If c_V is small, they can become comparable in height even at small mixing ratios. The large vulnerability is explained by a trapping of vacancies induced by the minority ions. Reasonable choices of model parameters yield typical behaviors found in experiments.Comment: 4 pages, 4 figure

Ignition of flammable hydrogen/air mixtures by high mass mechanical impact of Magnox contaminated surfaces

Magnox and its corrosion products are a major constituent of some legacy nuclear waste storage silos which generate hydrogen. An experimental study investigates the likelihood of ignition of hydrogen/air when large mass projectiles impact rusty surfaces with Magnox contamination. Ignition is observed with 50kg projectiles impacting a 45º Magnox-smeared rusty anvil plate with KE as low as 40J. Theoretical calculations relating to the angled impacts reveal that they involve substantial tangential energy losses associated with frictional heating of the impact surfaces. It is shown that these energy losses are particularly dependent on the shape of the projectile since projectile geometry determines the radius of gyration and the relationship of centre of gravity to the impact point. In conclusion, the projectile shape is likely to be of greater importance than the mass (i.e. for a given impact energy) because of its direct bearing on the magnitude of the tangential energy loss

Assessing identity, phenotype, and fate of endothelial progenitor cells

From the paradigm shifting observations of Harvey, Malpighi, and van Leeuwenhoek, blood vessels have become recognized as distinct and dynamic tissue entities that merge with the heart to form a closed circulatory system.1 Vessel structures are comprised predominantly of a luminal layer of endothelial cells that is surrounded by some form of basement membrane, and mural cells (pericytes or vascular smooth muscle cells) that make up the vessel wall. In larger more complex vessel structures the vessel wall is composed of a complex interwoven matrix with nerve components. Understanding the cellular and molecular basis for the formation, remodeling, repair, and regeneration of the vasculature have been and continue to be popular areas for investigation. The endothelium has become a particularly scrutinized cell population with the recognition that these cells may play important roles in maintaining vascular homeostasis and in the pathogenesis of a variety of diseases.2 Although it has been known for several decades that some shed or extruded endothelial cells enter the circulation as apparent contaminants in the human blood stream,3 only more recent technologies have permitted the identification of not only senescent sloughed endothelial cells,4 but also endothelial progenitor cells (EPCs), which have been purported to represent a normal component of the formed elements of circulating blood5 and play roles in disease pathogenesis.6–9 Most citations refer to an article published in 1997 in which Asahara and colleagues isolated, characterized, and examined the in vivo function of putative EPCs from human peripheral blood as a major impetus for generating interest in the field.10 This seminal article presented some evidence to consider emergence of a new paradigm for the process of neovascularization in the form of postnatal vasculogenesis. Since publication of that article, interest in circulating endothelial cells, and particularly EPCs, has soared, and one merely has to type the keyword search terms, endothelial progenitor cell, to recover more than 8984 articles including 1347 review articles in PubMed (as of June 2008). What can we possibly add in the form of another EPC review that will be considered of significant value for the reader? We will attempt to review some of the early article in the field and reflect on how information in those articles was gradually derivatized into perhaps more conflicting rather than unifying concepts. We will also attempt to concisely address some of the important determinants and principles that are now leading to a new understanding of what functionally constitutes an EPC and outline some of the current measures used to identify, enumerate, and quantify these cells. Finally, we give our opinion of the best definition for an EPC based on some comparative analyses performed primarily in human subjects

Pregnancy- and lactation related folate deficiency in South Africa - a case for folate food fortification

Objective. Characterisation of patients presenting with megaloblastic anaemia according to clinical, sociological, haematological and aetiological aspects of their disease, and use of these findings to increase awareness among clinicians and to make recommendations regarding changes in national health policy.Methods. This study included 104 patients presenting with megaloblastic anaemia to a large referral.hospital over a 1year period. Data were collected and analysed in terms of age, gender, parity, gravidity, duration of lactation, socioeconomic status, geographical origins, diet, previous haematinic treatment, clinical presentation and haematological measurements.Results. The most common cause of megaloblastic anaemia was pernicious anaemia or probable pernicious anaemia (50%), followed by pregnancy- and lactation-related folate deficiency (32%); of these patients, the majority (28) presented postpartum while lactating; 5 patients were in the immediate puerperal period of 6 weeks, and a further 16 were seen during the first year and 7 during the second year following' delivery. Only 4 patients were pregnant, and it is noteworthy that 2 of these were still lactating at 34 weeks' gestation.Conclusion. Pregnancy- and lactation-related folate deficiency up to 2 years after delivery remains a common cause of megaloblastic anaemia in South Africa. Certain communities in rural South Africa have recently been shown to have high incidences of both neural tube defects and folate deficiency. The fortification of a staple food (e.g. maize or flour) with folic acid is feasible, inexpensive, safe and likely to be beneficial. This practice should reduce the prevalences of megaloblastic anaemia in fertile women, neural tube defects, other congenital abnormalities, intra-uterine growthretardation, prematurity and possibly cardiovascular disease. There is urgent need for a national policy in this regard

Detection of Very Low-Frequency Quasi-Periodic Oscillations in the 2015 Outburst of V404 Cygni

In June 2015, the black hole X-ray binary (BHXRB) V404 Cygni went into outburst for the first time since 1989. Here, we present a comprehensive search for quasi-periodic oscillations (QPOs) of V404 Cygni during its recent outburst, utilizing data from six instruments on board five different X-ray missions: Swift/XRT, Fermi/GBM, Chandra/ACIS, INTEGRAL's IBIS/ISGRI and JEM-X, and NuSTAR. We report the detection of a QPO at 18 mHz simultaneously with both Fermi/GBM and Swift/XRT, another example of a rare but slowly growing new class of mHz-QPOs in BHXRBs linked to sources with a high orbital inclination. Additionally, we find a duo of QPOs in a Chandra/ACIS observation at 73 mHz and 1.03 Hz, as well as a QPO at 136 mHz in a single Swift/XRT observation that can be interpreted as standard Type-C QPOs. Aside from the detected QPOs, there is significant structure in the broadband power, with a strong feature observable in the Chandra observations between 0.1 and 1 Hz. We discuss our results in the context of current models for QPO formation.Comment: 17 pages, 9 figures, published in Ap

CFD Modelling coupled with Floating Structures and Mooring Dynamics for Offshore Renewable Energy Devices using the Proteus Simulation Toolkit

This is the author accepted manuscript. The final version is available from EWTEC via the link in this record.In this work, the coupling of novel opensource tools for simulating two-phase incompressible flow problems with fluid-structure interaction and mooring dynamics is presented. The open-source Computational Fluid Dynamics (CFD) toolkit Proteus is used for the simulations. Proteus solves the twophase Navier-Stokes equations using the Finite Element Method (FEM) and is fully coupled with an Arbitrary Lagrangian-Eulerian (ALE) formulation for mesh motion allowing solid body motion within the fluid domain. The multi-body dynamics solver, Chrono, is used for calculating rigid body motion and modelling dynamics of complex mooring systems. At each time step, Proteus computes the forces from the fluid acting on the rigid body necessary to find its displacement with Chrono which will be used as boundary conditions for mesh motion. Several verification and validation cases are presented here in order to prove the successful coupling between the two toolkits aforementioned. These test cases include wave sloshing in a tank, floating body dynamics under free and wave-induced motion for different degrees of freedom (DOFs), and mooring dynamics using beam element theory coupled with rigid body dynamics and collision detection. The successful validation of each component shows the potential of the coupled methodology to be used for assisting the design of offshore renewable energy devices.Support for this work was given by the Engineer Research and Development Center (ERDC) and HR Wallingford through the collaboration agreement (Contract No. W911NF-15-2-0110). The authors also acknowledge support for the IDCORE program from the Energy Technologies Institute and the Research Councils Energy Programme (grant number EP/J500847/)