Observations of the structure and evolution of solar flares with a soft X-ray telescope

Soft X ray flare events were observed with the S-056 X-ray telescope that was part of the ATM complement of instruments aboard SKYLAB. Analyses of these data are reported. The observations are summarized and a detailed discussion of the X-ray flare structures is presented. The data indicated that soft X-ray emitted by a flare come primarily from an intense well-defined core surrounded by a region of fainter, more diffuse emission. An analysis of flare evolution indicates evidence for preliminary heating and energy release prior to the main phase of the flare. Core features are found to be remarkably stable and retain their shape throughout a flare. Most changes in the overall configuration seem to be result of the appearance, disappearance or change in brightness of individual features, rather than the restructuring or reorientation of these features. Brief comparisons with several theories are presented

Universal quantum computation by discontinuous quantum walk

Quantum walks are the quantum-mechanical analog of random walks, in which a quantum `walker' evolves between initial and final states by traversing the edges of a graph, either in discrete steps from node to node or via continuous evolution under the Hamiltonian furnished by the adjacency matrix of the graph. We present a hybrid scheme for universal quantum computation in which a quantum walker takes discrete steps of continuous evolution. This `discontinuous' quantum walk employs perfect quantum state transfer between two nodes of specific subgraphs chosen to implement a universal gate set, thereby ensuring unitary evolution without requiring the introduction of an ancillary coin space. The run time is linear in the number of simulated qubits and gates. The scheme allows multiple runs of the algorithm to be executed almost simultaneously by starting walkers one timestep apart.Comment: 7 pages, revte

Development of an interatomic potential for the simulation of defects, plasticity, and phase transformations in titanium

New interatomic potentials describing defects, plasticity, and high temperature phase transitions for Ti are presented. Fitting the martensitic hcp-bcc phase transformation temperature requires an efficient and accurate method to determine it. We apply a molecular dynamics method based on determination of the melting temperature of competing solid phases, and Gibbs-Helmholtz integration, and a lattice-switch Monte Carlo method: these agree on the hcp-bcc transformation temperatures to within 2 K. We were able to develop embedded atom potentials which give a good fit to either low or high temperature data, but not both. The first developed potential (Ti1) reproduces the hcp-bcc transformation and melting temperatures and is suitable for the simulation of phase transitions and bcc Ti. Two other potentials (Ti2 and Ti3) correctly describe defect properties and can be used to simulate plasticity or radiation damage in hcp Ti. The fact that a single embedded atom method potential cannot describe both low and high temperature phases may be attributed to neglect of electronic degrees of freedom, notably bcc has a much higher electronic entropy. A temperature-dependent potential obtained from the combination of potentials Ti1 and Ti2 may be used to simulate Ti properties at any temperature.</p

Eye movements during scene inspection: A test of the saliency map hypothesis

What attracts attention when we inspect a scene? Two experiments recorded eye movements while viewers inspected pictures of natural office scenes in which two objects of interest were placed. One object had low contour density and uniform colouring (a piece of fruit), relative to another that was visually complex (for example, coffee mugs and commercial packages). In each picture the visually complex object had the highest visual saliency according to the Itti and Koch algorithm. Two experiments modified the task while the pictures were inspected, to determine whether visual saliency is invariably dominant in determining the pattern of fixations, or whether the purpose of inspection can provide a cognitive override that renders saliency secondary. In the first experiment viewers inspected the scene in preparation for a memory task, and the more complex objects were potent in attracting early fixations, in support of a saliency map model of scene inspection. In the second experiment viewers were set the task of detecting the presence of a low saliency target, and the effect of a high saliency distractor was negligible, supporting a model in which the saliency map can be built with cognitive influences that override low-level visual features

Ruby-throated Hummingbird, Archilochus colubris, Entanglements in Burdock, Arctium spp., at Delta Marsh, Manitoba

Exotic burdock (Arctium spp.) pose a risk of mortality for small native birds, such as the Ruby-throated Hummingbird (Archilochus colubris), which may become entangled in its burrs. At Delta Marsh, Manitoba, we found 11 hummingbirds and five individuals of four species of songbirds entangled on burdock in the dune-ridge forest over a 20-year period. Entangled birds were mostly migrants. Most hummingbirds caught were juvenile males, whereas the few songbirds were mostly adult males. We suspect that hummingbird entanglements resulted from an attraction to the purple flowers of burdock, but aggressive interactions with conspecifics and other factors may have been involved. Birds may be at a higher risk of entanglement at important migratory stopover sites, such as Delta Marsh, where both burdock and large numbers of birds are concentrated in a small area

Probiotic administration in congenital heart disease: a pilot study.

ObjectiveTo investigate the impact of probiotic Bifidobacterium longum ssp. infantis on the fecal microbiota and plasma cytokines in neonates with congenital heart disease.Study designSixteen infants with congenital heart disease were randomly assigned to receive either B. infantis (4.2 × 10(9) colony-forming units two times daily) or placebo for 8 weeks. Stool specimens from enrolled infants and from six term infants without heart disease were analyzed for microbial composition. Plasma cytokines were analyzed weekly in the infants with heart disease.ResultsHealthy control infants had increased total bacteria, total Bacteroidetes and total bifidobacteria compared to the infants with heart disease, but there were no significant differences between the placebo and probiotic groups. Plasma interleukin (IL)10, interferon (IFN)γ and IL1β levels were transiently higher in the probiotic group.ConclusionCongenital heart disease in infants is associated with dysbiosis. Probiotic B. infantis did not significantly alter the fecal microbiota. Alterations in plasma cytokines were found to be inconsistent

Visual saliency and semantic incongruency influence eye movements when inspecting pictures

Models of low-level saliency predict that when we first look at a photograph our first few eye movements should be made towards visually conspicuous objects. Two experiments investigated this prediction by recording eye fixations while viewers inspected pictures of room interiors that contained objects with known saliency characteristics. Highly salient objects did attract fixations earlier than less conspicuous objects, but only in a task requiring general encoding of the whole picture. When participants were required to detect the presence of a small target, then the visual saliency of nontarget objects did not influence fixations. These results support modifications of the model that take the cognitive override of saliency into account by allowing task demands to reduce the saliency weights of task-irrelevant objects. The pictures sometimes contained incongruent objects that were taken from other rooms. These objects were used to test the hypothesis that previous reports of the early fixation of congruent objects have not been consistent because the effect depends upon the visual conspicuity of the incongruent object. There was an effect of incongruency in both experiments, with earlier fixation of objects that violated the gist of the scene, but the effect was only apparent for inconspicuous objects, which argues against the hypothesis