Evaluation of center-line extraction algorithms in quantitative coronary angiography

Objective testing of centerline extraction accuracy in quantitative coronary angiography (QCA) algorithms is a very difficult task. Standard tools for this task are not yet available. We present a simulation tool that generates synthetic angiographic images of a single coronary artery with predetermined centerline and diameter function. This simulation tool was used creating a library of images for the objective comparison and evaluation of QCA algorithms. This technique also provides the means for understanding the relationship between the algorithms' performance and limitations and the vessel's geometrical parameters. In this paper, two algorithms are evaluated and the results are presented.     

Calculation of the mutual induction between coplanar circularsurface coils in magnetic resonance imaging

The induced current in a coil due to the presence of alternating currents in an adjacent coil is calculated here for a case of two similar and coplanar, circular coils. By using an overlapping configuration, the mutual inductance is nullified as is predicted theoretically and confirmed experimentally.     

The composite structure of peak 5 in the glow curve of LiF:Mg,Ti (TLD-100): confirmation of peak 5a arising from a locally trapped electron-hole configuration

The hypothesis that glow peak 5a arises from localised e-h capture is confirmed by the following experimental observations: (i) The high conversion efficiency (CE) (CE5a-->4 = 3 +/- 0.5) of peak 5a to peak 4 (a hole-only trap) deduced from detailed Im-Tstop optical bleaching studies at 310 nm compared to the much lower CE of peak 5 (an electron-only trap) (CE5-->4 = 0.0026+/-0.012). (ii) The lack of an increase in the sensitivity of glow peak 5a following 2.6 MeV and 6.8 MeV He ion irradiation in 'sensitised' material compared to the factor two increase in the sensitivity of peak 5; (S/S0)5a = 0.86+/-0.12, compared to (S/S0)5 = 2.0+/-0.2. (iii) The late entry into saturation of the 2.6 MeV and 6.8 MeV He ion TL-fluence response curves for peak 5a compared to peak 5 in sensitised and normal material resulting in the following values for the track radial saturation parameter: (r50)5a = 100+/-20) Angstroms compared to (r50)5 = 380+/-30 Angstroms. (iv) The low value of 0.1 for the 'track-escape' parameter of peak 5a deduced from the Extended Track Interaction Model analysis of He ion TL fluence response compared to order of magnitude greater values for peaks 5 and 5b.     

Overexpression of UBA5 in Cells Mimics the Phenotype of Cells Lacking UBA5

Ufmylation is a posttranslational modification in which the modifier UFM1 is attached to target proteins. This conjugation requires the concerted work of three enzymes named UBA5, UFC1, and UFL1. Initially, UBA5 activates UFM1 in a process that ends with UFM1 attached to UBA5’s active site Cys. Then, in a trans-thiolation reaction, UFM1 is transferred from UBA5 to UFC1, forming a thioester bond with the latter. Finally, with the help of UFL1, UFM1 is transferred to the final destination—a lysine residue on a target protein. Therefore, not surprisingly, deletion of one of these enzymes abrogates the conjugation process. However, how overexpression of these enzymes affects this process is not yet clear. Here we found, unexpectedly, that overexpression of UBA5, but not UFC1, damages the ability of cells to migrate, in a similar way to cells lacking UBA5 or UFC1. At the mechanistic level, we found that overexpression of UBA5 reverses the trans-thiolation reaction, thereby leading to a back transfer of UFM1 from UFC1 to UBA5. This, as seen in cells lacking UBA5, reduces the level of charged UFC1 and therefore harms the conjugation process. In contrast, co-expression of UBA5 with UFM1 abolishes this effect, suggesting that the reverse transfer of UFM1 from UFC1 to UBA5 depends on the level of free UFM1. Overall, our results propose that the cellular expression level of the UFM1 conjugation enzymes has to be tightly regulated to ensure the proper directionality of UFM1 transfer.     

Periodic propagation of localized compaction in a brittle granular material

Experiments that involve the monotonic compression of granular packs composed of brittle porous grains in a piston-die press reveal evidence of a localized compaction band that propagates periodically within the specimen opposite to the direction of loading and faster than the imposed specimen shortening rate.     

Children's use of the temporal dimension of gaze for inferring preference.

This study examined 4- and 5-year-olds' ability to spontaneously use the relative duration and frequency of another's object-directed gaze for inferring that person's preference. In Experiment 1, analysis revealed a strong age effect for judgment accuracy, which could not be accounted for by cue-monitoring proficiency. Reducing the saliency of the objects in Experiment 2 yielded significant improvement in the younger children's performance. Thus, at 4 years, children already show signs of attending to the temporal dimension of gaze for making mentalistic inferences of preferential liking, but their competence may be undermined by the object choices themselves. By 5 years, they appear to overcome this competition. The obtained developmental difference is discussed in terms of concurrent transitions in attention regulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A heterarchical multiscale model for granular materials with evolving grainsize distribution

Naturally occurring granular flows, such as landslides, debris flows and avalanches typically have size ratios of up to \(10^{6}\) between the smallest and largest constituent particles. For the purposes of modelling, however, it is generally assumed that a single representative size can adequately describe the grains. Polydisperse flows are not described more completely primarily because of two reasons: The first is a lack of understanding of the physical mechanisms which affect polydisperse flows. The second is a lack of models with which to describe such systems. Here, we present a heterarchical multiscale model which accounts for both the microstructural evolution within representative elementary volumes, and also the associated changes in bulk flow properties. Three key mechanisms are addressed; segregation, comminution and mixing. Granular segregation is an important mechanism for industrial processes aiming at mixing grains. Additionally, it plays a pivotal role in determining the kinematics of geophysical flows. Because of segregation, the grainsize distribution in a granular medium varies in space and time during flow. Additional complications arise from the presence of comminution, where new particles are created, potentially enhancing segregation. This has a feedback on the comminution process, as particles change their local neighbourhood. Simultaneously, particles are generally undergoing remixing, further complicating the segregation and comminution processes. The interaction between these mechanisms is explored using a stochastic lattice model with three rules: one for each of segregation, comminution and mixing. The interplay between these rules creates complex patterns, as seen in segregating systems, and depth dependent log-normal grading curves, which have been observed in avalanche runout.     

Soil mechanics: breaking ground

In soil mechanics, student's models are classified as simple models that teach us unexplained elements of behaviour; an example is the Cam clay constitutive models of critical state soil mechanics (CSSM). 'Engineer's models' are models that elaborate the theory to fit more behavioural trends; this is usually done by adding fitting parameters to the student's models. Can currently unexplained behavioural trends of soil be explained without adding fitting parameters to CSSM models, by developing alternative student's models based on modern theories?Here I apply an alternative theory to CSSM, called 'breakage mechanics', and develop a simple student's model for sand. Its unique and distinctive feature is the use of an energy balance equation that connects grain size reduction to consumption of energy, which enables us to predict how grain size distribution (gsd) evolves-an unprecedented capability in constitutive modelling. With only four parameters, the model is physically clarifying what CSSM cannot for sand: the dependency of yielding and critical state on the initial gsd and void ratio.