Reinforced carbon-carbon oxidation behavior in convective and radiative environments

Reinforced carbon-carbon, which is used as thermal protection on the space shuttle orbiter wing leading edges and nose cap, was tested in both radiant and plasma arcjet heating test facilities. The test series was conducted at varying temperatures and pressures. Samples tested in the plasma arcjet facility had consistently higher mass loss than those samples tested in the radiant facility. A method using the mass loss data is suggested for predicting mission mass loss for specific locations on the Orbiter

Synthetic Turing protocells: vesicle self-reproduction through symmetry-breaking instabilities

The reproduction of a living cell requires a repeatable set of chemical events to be properly coordinated. Such events define a replication cycle, coupling the growth and shape change of the cell membrane with internal metabolic reactions. Although the logic of such process is determined by potentially simple physico-chemical laws, the modeling of a full, self-maintained cell cycle is not trivial. Here we present a novel approach to the problem which makes use of so called symmetry breaking instabilities as the engine of cell growth and division. It is shown that the process occurs as a consequence of the breaking of spatial symmetry and provides a reliable mechanism of vesicle growth and reproduction. Our model opens the possibility of a synthetic protocell lacking information but displaying self-reproduction under a very simple set of chemical reactions

CYCLICAL CONCENTRATION AND CONSOLIDATION IN BIOTECH R&D: A NEO-SCHUMPETERIAN MODEL

Over the past fifteen years, the agricultural biotechnology industry has exhibited cyclical behavior in concentration and consolidation. This paper provides a theoretical model of endogenous R&D, in which industry concentration exhibits cyclical behavior. The model also generates additional testable hypotheses, and policy implications.Industrial Organization, Research and Development/Tech Change/Emerging Technologies,

Plasma exchange and intravenous immunoglobulin for the peri‐operative management of type 2 heparin‐induced thrombocytopaenia in a patient requiring urgent surgery for critical limb ischaemia

Summary: We report the case of a 61‐year‐old female who developed heparin‐induced thrombocytopaenia following treatment of a submassive pulmonary embolism, and who then required an above knee amputation for critical limb ischaemia. Heparin‐induced thrombocytopaenia is a rare, immune‐mediated complication associated with an in‐hospital mortality rate of 10%. It is more common in surgical patients, with patients undergoing orthopaedic surgery more likely to develop it than patients undergoing cardiac surgery, but heparin‐dependent immunoglobulin G antibodies are more likely to be formed in the latter. Peri‐operative management remains a challenge. Ideally, it is preferable to wait for the platelet count to improve; but in certain cases, surgery cannot be delayed. Heparin‐induced thrombocytopaenia is usually managed with direct thrombin inhibitors, such as argatroban and bivalirudin. Newer therapeutic modalities, such as plasmapheresis and intravenous immunoglobulin, as used in this case, can rapidly remove antibodies, but the certainty of evidence is low. Our case adds to the literature regarding the use of these modalities and highlights the multidisciplinary team approach required to manage such complex cases

Waste Heat Recovery from Underground Railways – Evaluating the Cooling Potential

The Bunhill Waste Heat Recovery (WHR) System is a first of its kind scheme that will recover waste energy from a ventilation shaft of the London Underground (LU) network. The system is based upon the installation of a heat recovery heat exchanger that consists of cooling coils and a reversible fan. The coils are connected to a heat pump that supplies low carbon thermal energy to the Bunhill Heat Network in the London Borough of Islington. One particularly important aspect of the Bunhill WHR system is its ability to operate in a way that not only provides heating to the local heat network, but can also simultaneously supply cooled air to the LU tunnels depending on the operation of the reversible fan. The current paper provides an analysis of the heating and cooling duties and their associated cost and carbon savings against conventional technologies based upon a mathematical model of the WHR system. The model is able to predict the condition of the coil surface according to air inlet parameters, and this is used to calculate the latent and sensible cooling loads, which are applied to simulate how the system impacts the local tunnel environment, with peak temperature reductions of up to 7.2 °C being estimated for adjacent stations in 2030. The results from these analyses are reported, together with recommendations for further development and future deployment of heat recovery from metro systems

Three-dimensional MHD Simulations of Jets from Accretion Disks

We report the results of 3-dimensional magnetohydrodynamic (MHD) simulations of a jet formation by the interaction between an accretion disk and a large scale magnetic field. The disk is not treated as a boundary condition but is solved self-consistently. To investigate the stability of MHD jet, the accretion disk is perturbed with a non-axisymmetric sinusoidal or random fluctuation of the rotational velocity. The dependences of the jet velocity $(v_z)$, mass outflow rate $(\dot{M}_w)$, and mass accretion rate $(\dot{M}_a)$ on the initial magnetic field strength in both non-axisymmetric cases are similar to those in the axisymmetric case. That is, $v_z \propto B_0^{1/3}$, $\dot{M}_w \propto B_0$ and $\dot{M}_a \propto B_0^{1.4}$ where $B_0$ is the initial magnetic field strength. The former two relations are consistent with the Michel's steady solution, $v_z \propto (B_0^2/\dot{M}_w)^{1/3}$, although the jet and accretion do not reach the steady state. In both perturbation cases, a non-axisymmetric structure with $m=2$ appears in the jet, where $m$ means the azimuthal wave number. This structure can not be explained by Kelvin-Helmholtz instability and seems to originate in the accretion disk. Non-axisymmetric modes in the jet reach almost constant levels after about 1.5 orbital periods of the accretion disk, while all modes in the accretion disk grow with oscillation. As for the angular momentum transport by Maxwell stress, the vertical component, $$, is comparable to the radial component,$$, in the wide range of initial magnetic field strength.Comment: Accepted for publication in ApJ. The pdf file with high resolution figures can be downloaded at http://www.kusastro.kyoto-u.ac.jp/~hiromitu/3j050806.pd

Geographical information retrieval with ontologies of place

Geographical context is required of many information retrieval tasks in which the target of the search may be documents, images or records which are referenced to geographical space only by means of place names. Often there may be an imprecise match between the query name and the names associated with candidate sources of information. There is a need therefore for geographical information retrieval facilities that can rank the relevance of candidate information with respect to geographical closeness of place as well as semantic closeness with respect to the information of interest. Here we present an ontology of place that combines limited coordinate data with semantic and qualitative spatial relationships between places. This parsimonious model of geographical place supports maintenance of knowledge of place names that relate to extensive regions of the Earth at multiple levels of granularity. The ontology has been implemented with a semantic modelling system linking non-spatial conceptual hierarchies with the place ontology. An hierarchical spatial distance measure is combined with Euclidean distance between place centroids to create a hybrid spatial distance measure. This is integrated with thematic distance, based on classification semantics, to create an integrated semantic closeness measure that can be used for a relevance ranking of retrieved objects

Loop colostomies are safe in anorectal malformations

Aim of the study: Divided colostomy (DC) has been recommended in anorectal malformations (ARMs) with previously reported advantages of decreasing overflow into the distal limb and urinary tract infections (UTIs). Skin bridge loop colostomy (LC) is a technically easier alternative without an increase in these complications. We report our institutional experience of LC in ARM. Methods: Retrospective study (Institution-approved Clinical Audit) reviewing the clinical records of all patients with ARM undergoing stoma formation in a single UK tertiary pediatric surgical center (2000–2015). Data collected included type of ARM, associated anomalies, type and level of colostomy, time to stoma closure, complications and UTIs. Results: One hundred and eighty-two (95 female) patients underwent colostomy formation for ARM. The vast majority (171/ 94%) underwent LC; 9 (5%) had a divided colostomy (DC) and 2 (1%) had no available data. The spectrum of defects in girls included rectovestibular (62/65%), rectovaginal (4/4%) and cloaca (29/31%). In boys, 71 (82%) had a fistula to the urinary tract and 16 (18%) presented with a perineal fistula. Urological abnormalities coexisted in 87 (47.8%) patients. Thirty five (21%) patients developed UTIs. Among the 19 girls who developed UTI, 8 had rectovestibular fistula and 11 had cloaca. Of the 16 boys who developed UTI, 14 had a fistula to the urinary tract and 11 had an independent urological abnormality. The mean time from stoma formation to stoma closure was 10 (3–52) months. Complications were reported in 22 (12%) LCs. Fifteen patients (9%) developed a stoma prolapse following LC with 10 (6%) requiring surgical revision. Conclusions: This is the largest reported series of outcomes following LC for ARM. LC is easier to perform and to close, requiring minimal surgical access, with comparable complications and outcomes to those published for DC. Type of study: Retrospective comparative study. Level of evidence: III