7,872 research outputs found
Convectiveâreactive nucleosynthesis of K, Sc, Cl and p-process isotopes in OâC shell mergers
© 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. We address the deficiency of odd-Z elements P, Cl, K and Sc in Galactic chemical evolution models through an investigation of the nucleosynthesis of interacting convective O and C shells in massive stars. 3D hydrodynamic simulations of O-shell convection with moderate C-ingestion rates show no dramatic deviation from spherical symmetry. We derive a spherically averaged diffusion coefficient for 1D nucleosynthesis simulations, which show that such convective-reactive ingestion events can be a production site for P, Cl, K and Sc. An entrainment rate of 10-3Mâs-1features overproduction factors OPsâ 7. Full O-C shell mergers in our 1D stellar evolution massive star models have overproduction factors OPm> 1 dex but for such cases 3D hydrodynamic simulations suggest deviations from spherical symmetry. Îł - process species can be produced with overproduction factors of OPm> 1 dex, for example, for130, 132Ba. Using the uncertain prediction of the 15Mâ, Z = 0.02 massive star model (OPmâ 15) as representative for merger or entrainment convective-reactive events involving O- and C-burning shells, and assume that such events occur in more than 50 per cent of all stars, our chemical evolution models reproduce the observed Galactic trends of the odd-Z elements
Non equilibrium thermodynamics and cosmological pancakes formation
We investigate the influence of non equilibrium thermodynamics on
cosmological structure formation. In this paper, we consider the collapse of
planar perturbations usually called "Zel'dovich pancakes". We have developed
for that purpose a new two fluids (gas and dark matter) hydrodynamical code,
with three different thermodynamical species: electrons, ions and neutral
particles (T_e\ne T_i \ne T_n). We describe in details the complex structure of
accretion shock waves. We include several relevant processes for a low density,
high temperature, collisional plasma such as non-equilibrium chemical
reactions, cooling, shock heating, thermal energy equipartition between
electrons, ions and neutral particles and electronic conduction. We find two
different regions in the pancake structure: a thermal precursor ahead of the
compression front and an equipartition wave after the compression front where
electrons and ions temperatures differ significantly. This complex structure
may have two interesting consequences: pre-heating of unshocked regions in the
vicinity of massive X-ray clusters and ions and electrons temperatures
differences in the outer regions of X-rays clusters.Comment: 30 pages, including 8 figures, accepted for publication in The
Astrophysical Journa
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The ConStratO model of handover: a tool to support technology design and evaluation
Handovers are a specific kind of multidisciplinary team meeting. Shift handovers and transfers are both regular features of hospital work but there is currently great variation in how such handovers are conducted, presenting a challenging for those seeking to develop technology to support handover. This paper presents the ConStratO model of handover, which captures aspects of the context that influence how the handover is conducted, a range of different handover strategies relating to different aspects of the handover, and possible outcomes of handover. The model is based on detailed data collection in a range of clinical settings. We present the model as a tool for developing and evaluating technology support for handover
Longitudinal and Transverse Response Functions in ^(56)Fe(e,e') at Momentum Transfer near 1 GeV/c
Inclusive electron-scattering cross sections have been measured for ^(56)Fe in the quasielastic region at electron energies between 0.9 and 4.3 GeV, at scattering angles of 15° and 85°. Longitudinal and transverse response functions at a q of 1.14 GeV/c have been extracted using a Rosenbluth separation. The experimental Coulomb sum has been obtained with aid of an extrapolation. The longitudinal response function, after correction for Coulomb distortion, is lower than quasifree-scattering-model predictions at the quasielastic peak and on the high-Ï side
The Organic Research Centre; Elm Farm Bulletin 84 July 2006
Regular bulletin with technical updates of the Organic Advisory Service
Issue contains:
Battling on for Avian Flu preventive vaccination; Organic Colombian Blacktail eggs;
UK Co-existence - GMOand non-GMO crops; Aspects of Poultry Behaviour; CAP in the service of biodiversity; Seeing the Wood, the Trees and the Catch 22; Beware of organic market "statistics"; A central role in energy review
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Safe use of symbols in handover documentation for medical teams
Concern has been reported about the safe use of medical abbreviations in documents such as handover sheets and medical notes, especially when information is being communicated between staff of different specialties (BBC 2008, Sheppard et al. 2008). This article describes a study to investigate whether the use of symbols in handover documentation that is shared within and between multidisciplinary teams (MDTs) has similar safety implications. We asked 19 healthcare professionals from a range of specialties to identify 45 different combinations of 38 individual symbols. The symbols and combinations of symbols were extracted from 102 handover sheets taken from 6 different healthcare contexts in 4 London hospitals. Three symbols proposed in Microsoft's Common User Interface guidelines for alert symbols were also included. Results reveal that while some symbols are well understood, many others are either ambiguous or unknown. These results have implications for the safe use of symbols in medical documents, including paper and electronic handover documents and Electronic Patient Records (EPRs), especially where teams comprise individuals from different professional backgrounds, i.e. MDTs. We offer initial suggestions for standardisation and further research
Octahedral Tilt Instability of ReO_3-type Crystals
The octahedron tilt transitions of ABX_3 perovskite-structure materials lead
to an anti-polar (or antiferroelectric) arrangement of dipoles, with the low
temperature structure having six sublattices polarized along various
crystallographic directions. It is shown that an important mechanism driving
the transition is long range dipole-dipole forces acting on both displacive and
induced parts of the anion dipole. This acts in concert with short range
repulsion, allowing a gain of electrostatic (Madelung) energy, both
dipole-dipole and charge-charge, because the unit cell shrinks when the hard
ionic spheres of the rigid octahedron tilt out of linear alignment.Comment: 4 page with 3 figures included; new version updates references and
clarifies the argument
SeaWiFS technical report series. Volume 10: Modeling of the SeaWiFS solar and lunar observations
Post-launch stability monitoring of the Sea-viewing Wide Field-of-view Sensor (SeaWifs) will include periodic sweeps of both an onboard solar diffuser plate and the moon. The diffuser views will provide short-term checks and the lunar views will monitor long-term trends in the instrument's radiometric stability. Models of the expected sensor response to these observations were created on the SeaWiFS computer at the National Aeronautics and Space Administration's (NASA) Goddard Space Flight Center (GSFC) using the Interactive Data Language (IDL) utility with a graphical user interface (GUI). The solar model uses the area of intersecting circles to simulate the ramping of sensor response while viewing the diffuser. This model is compared with preflight laboratory scans of the solar diffuser. The lunar model reads a high-resolution lunar image as input. The observations of the moon are simulated with a bright target recovery algorithm that includes ramping and ringing functions. Tests using the lunar model indicate that the integrated radiance of the entire lunar surface provides a more stable quantity than the mean of radiances from centralized pixels. The lunar model is compared to ground-based scans by the SeaWiFS instrument of a full moon in December 1992. Quality assurance and trend analyses routines for calibration and for telemetry data are also discussed
Evolutionary origins and development of saw-teeth on the sawfish and sawshark rostrum (Elasmobranchii; Chondrichthyes)
A well-known characteristic of chondrichthyans (e.g. sharks, rays) is their covering of external skin denticles (placoid scales), but less well understood is the wide morphological diversity that these skin denticles can show. Some of the more unusual of these are the tooth-like structures associated with the elongate cartilaginous rostrum âsawâ in three chondrichthyan groups: Pristiophoridae (sawsharks; Selachii), Pristidae (sawfish; Batoidea) and the fossil Sclerorhynchoidea (Batoidea). Comparative topographic and developmental studies of the âsaw-teethâ were undertaken in adults and embryos of these groups, by means of three-dimensional-rendered volumes from X-ray computed tomography. This provided data on development and relative arrangement in embryos, with regenerative replacement in adults. Saw-teeth are morphologically similar on the rostra of the Pristiophoridae and the Sclerorhynchoidea, with the same replacement modes, despite the lack of a close phylogenetic relationship. In both, tooth-like structures develop under the skin of the embryos, aligned with the rostrum surface, before rotating into lateral position and then attaching through a pedicel to the rostrum cartilage. As well, saw-teeth are replaced and added to as space becomes available. By contrast, saw-teeth in Pristidae insert into sockets in the rostrum cartilage, growing continuously and are not replaced. Despite superficial similarity to oral tooth developmental organization, saw-tooth spatial initiation arrangement is associated with rostrum growth. Replacement is space-dependent and more comparable to that of dermal skin denticles. We suggest these saw-teeth represent modified dermal denticles and lack the âmany-for-oneâ replacement characteristic of elasmobranch oral dentitions
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