Evaluation of artery visualizations for heart disease diagnosis

Heart disease is the number one killer in the United States, and finding indicators of the disease at an early stage is critical for treatment and prevention. In this paper we evaluate visualization techniques that enable the diagnosis of coronary artery disease. A key physical quantity of medical interest is endothelial shear stress (ESS). Low ESS has been associated with sites of lesion formation and rapid progression of disease in the coronary arteries. Having effective visualizations of a patient's ESS data is vital for the quick and thorough non-invasive evaluation by a cardiologist. We present a task taxonomy for hemodynamics based on a formative user study with domain experts. Based on the results of this study we developed HemoVis, an interactive visualization application for heart disease diagnosis that uses a novel 2D tree diagram representation of coronary artery trees. We present the results of a formal quantitative user study with domain experts that evaluates the effect of 2D versus 3D artery representations and of color maps on identifying regions of low ESS. We show statistically significant results demonstrating that our 2D visualizations are more accurate and efficient than 3D representations, and that a perceptually appropriate color map leads to fewer diagnostic mistakes than a rainbow color map.     

Weak discontinuity annihilation in solidification modelling

Discontinuous behaviour provides substantial obstacles to the efficient application of mesh based numerical techniques. Accounting for strong discontinuities is presently of particular interest to the finite element research community with for example the development of cohesive and enriched elements to cater for material separation. Although strong discontinuities are of importance, of equal if not of greater interest and the focus in this paper, are weak discontinuities, which are present at any material change. A recent innovation for accounting for weak discontinuities has been the discovery of non-physical variables which are founded and defined using transport equations.This paper is concerned with the application of the non-physical approach to solidification modelling in the presence of more than one material discontinuity. A typical feature of the enthalpy-temperature response in solidification is discontinuities at phase transition temperatures as a consequence of phase change and latent heat release. In these circumstances, depending on the conditions that prevail, an element in a finite element mesh can have more than one discontinuity present.Presented in the paper is a methodology that can cater for multiple discontinuities. The non-physical approach permits the precise removal of weak discontinuities arising in the governing transport equations. In order to facilitate the application of the approach the finite element equations are presented in the form of weighted transport equations. The method utilises a non-physical form of enthalpy that possesses a remarkable source distribution like property at a discontinuity. It is demonstrated in the paper that it is through this property that multiple discontinuities can be exactly removed from an element so facilitating the use of continuous approximations.The new methodology is applied to a range of simple problems to provide an in-depth treatment and for ease of understanding to demonstrate the methods remarkable accuracy and stability.     

Isokinetic strength characteristics in wrist flexion and extension

A laboratory experiment was conducted to measure strength characteristics in dynamic (isokinetic) wrist flexion and extension. Twenty four college-age males exerted their maximum torque in both concentric flexion and extension at 60, 120, and 180°/s of angular velocity through a ±60° range of deviation from wrist neutral. Results show that velocity and motion direction significantly effected both peak torque as well as the postural displacement of peak torque. The value of peak torque decreased with an increase in velocity and the wrist angle at peak torque generally moved to a more deviated, flexed posture (from neutral) with increasing velocity as well. Peak torque for all velocity and motion-type conditions tested occurred in a flexed posture relative to neutral. It is anticipated that these results may be of use as biomechanically based considerations in the evaluation and design of upper extremity tasks involving wrist flexion/extension as well as to perhaps give insight into functional characteristics of the wrist. Finally, regression equations were developed to aid in the prediction of peak torque based upon task, individual and/or population parameters.

Relevance to industry

Results from this study should enhance the overall understanding of wrist functioning. Specifically, motion type, velocity of movement and wrist posture are important ergonomic design considerations. These results can also be used to modify existing biomechanical models that do not consider wrist variables.     

Building language resources for a Multi-Engine English-Filipino machine translation system

In this paper, we present the building of various language resources for a multi-engine bi-directional English-Filipino Machine Translation (MT) system. Since linguistics information on Philippine languages are available, but as of yet, the focus has been on theoretical linguistics and little is done on the computational aspects of these languages, attempts are reported here on the manual construction of these language resources such as the grammar, lexicon, morphological information, and the corpora which were literally built from almost non-existent digital forms. Due to the inherent difficulties of manual construction, we also discuss our experiments on various technologies for automatic extraction of these resources to handle the intricacies of the Filipino language, designed with the intention of using them for the MT system. To implement the different MT engines and to ensure the improvement of translation quality, other language tools (such as the morphological analyzer and generator, and the part of speech tagger) were developed.     

On the use of analytical expressions for the voltage distribution to analyze intracellular recordings

Different analytical expressions for the membrane potential distribution of membranes subject to synaptic noise have been proposed and can be very helpful in analyzing experimental data. However, all of these expressions are either approximations or limit cases, and it is not clear how they compare and which expression should be used in a given situation. In this note, we provide a comparison of the different approximations available, with an aim of delineating which expression is most suitable for analyzing experimental data.     

Conductivity measurements on liquid sulphur

The electrical conductivity of liquid sulphur has been measured from the melting point to 900° C, evaporation of the sulphur being prevented by use of an atmosphere of argon at elevated pressure. With rise in temperature, the conductivity increases except at the polymerization maximum near 170° C where a minimum in the conductivity is confirmed. Above 400° C the plot of log versus 1/T is linear, and on the assumption that the conductivity at these temperatures is intrinsic, a value of 3.1 eV is obtained for the energy gap. Although the rise in conductivity above 400° C is accompanied by a decrease in mean chain length in the liquid, there is no simple relationship between the two properties. The behaviour of sulphur is compared with that of liquid selenium.     

Impact of the Boeing 767 Aircraft into the World Trade Center

A numerical simulation of the aircraft impact into the exterior columns of the World Trade Center (WTC) was done using LS-DYNA. For simplification, the fuselage was modeled as a thin-walled cylinder, the wings were modeled as box beams with a fuel pocket, and the engines were represented as rigid cylinders. The exterior columns of the WTC were represented as box beams. Actual masses, material properties and dimensions of the Boeing 767 aircraft and the exterior columns of the WTC were used in this analysis. It was found that about 46% of the initial kinetic energy of the aircraft was used to damage columns. The minimum impact velocity of the aircraft to just penetrate the exterior columns would be 130?m/s. It was also found that a Boeing 767 traveling at top speed would not penetrate exterior columns of the WTC if the columns were thicker than 20?mm.