Multiloop algebras, iterated loop algebras and extended affine Lie algebras of nullity 2

Let M(n) be the class of all multiloop algebras of finite dimensional simple Lie algebras relative to n-tuples of commuting finite order automorphisms. It is a classical result that M(n) the class of all derived algebras modulo their centres of affine Kac-Moody Lie algebras. This combined with the Peterson-Kac conjugacy theorem for affine algebras results in a classification of the algebras in M(1). In this paper, we classify the algebras in M(2), and further determine the relationship between M(2) and two other classes of Lie algebras: the class of all loop algebras of affine Lie algebras and the class of all extended affine Lie algebras of nullity 2.Fil: Allison, Bruce. University of Alberta; CanadáFil: Berman, Stephen. No especifica;Fil: Pianzola, Arturo. University of Alberta; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Modeling the missile-launch tube problem in DYSCO

DYSCO is a versatile, general purpose dynamic analysis program which assembles equations and solves dynamics problems. The executive manages a library of technology modules which contain routines that compute the matrix coefficients of the second order ordinary differential equations of the components. The executive performs the coupling of the equations of the components and manages the solution of the coupled equations. Any new component representation may be added to the library if, given the state vector, a FORTRAN program can be written to compute M, C, K, and F. The problem described demonstrates the generality of this statement

Type-II Quantum Algorithms

We review and analyze the hybrid quantum-classical NMR computing methodology referred to as Type-II quantum computing. We show that all such algorithms considered so far within this paradigm are equivalent to some classical lattice-Boltzmann scheme. We derive a sufficient and necessary constraint on the unitary operator representing the quantum mechanical part of the computation which ensures that the model reproduces the Boltzmann approximation of a lattice-gas model satisfying semi-detailed balance. Models which do not satisfy this constraint represent new lattice-Boltzmann schemes which cannot be formulated as the average over some underlying lattice gas. We close the paper with some discussion of the strengths, weaknesses and possible future direction of Type-II quantum computing.Comment: To appear in Physica

Adenosine pharmacologic stress myocardial perfusion tomographic imaging in patients with significant aortic stenosis Diagnostic efficacy and comparison of clinical, hemodynamic and electrocardiographic variables with 100 age-matched control subjects

AbstractObjectives. This study assessed the safety and diagnostic accuracy of adenosine stress myocardial perfusion scintigraphy for the detection of coronary artery disease using single-photon emission computed tomography (SPECT) in patients with significant aortic stenosis.Background. Exercise cardiac stress testing in patients with significant aortic stenosis is generally avoided because of concerns for safety. In addition, those studies that have analyzed the utility of exercise testing both with and without myocardial thallium-201 scintigraphy for the diagnosis of coronary artery disease have yielded low specificity. Currently, no safe and accurate means exists to noninvasively assess the presence, extent and severity of coronary artery disease in patients with significant aortic stenosis.Methods. The study included 35 patients with moderate to severe aortic stenosis (mean [±SD] aortic valve area 0.84 ± 0.16 cm2, range 0.5 to 1.2; mean maximal instantaneous aortic valve gradient 44.4 ± 15.9 mm Hg, range 20 to 84). All patients underwent a 6-min adenosine infusion (140 μg/kg body weight per min) protocol and either separate acquisition rest thallium-201/stress technetium-99m sestamibi or stress and 4-h redistribution thallium-201 SPECT. Visual 20-segment SPECT analysis used a standard five-point scoring system from 0 (normal tracer uptake) to 4 (absent uptake). The SPECT results were considered abnormal if more than two segments had a stress score ≥2. Hemodynamic, electrocardiographic and clinical responses were compared with those in a reference group of 100 consecutive age-matched patients undergoing adenosine SPECT who did not have aortic stenosis.Results. Hemodynamic responses during adenosine stress testing between the study and control patients demonstrated no significant difference in the net change in systolic blood pressure (18% of baseline vs. 14%, patients with aortic stenosis vs. control subjects), heart rate (21% vs. 19%), rate-pressure product (0% vs. 2%) or incidence of chest pain (23% vs. 35%) or transient second- (9% vs. 9%) or third-degree atrioventricular block (3% vs. 1%). In the 20 patients who had coronary angiography, sensitivity for detection of coronary artery disease was 92% (12 of 13) and specificity was 71% (5 of 7).Conclusions. In this preliminary study, adenosine was found to be well tolerated and diagnostically accurate in patients with moderate to severe aortic stenosis

Scientific Workflow Applications on Amazon EC2

The proliferation of commercial cloud computing providers has generated significant interest in the scientific computing community. Much recent research has attempted to determine the benefits and drawbacks of cloud computing for scientific applications. Although clouds have many attractive features, such as virtualization, on-demand provisioning, and "pay as you go" usage-based pricing, it is not clear whether they are able to deliver the performance required for scientific applications at a reasonable price. In this paper we examine the performance and cost of clouds from the perspective of scientific workflow applications. We use three characteristic workflows to compare the performance of a commercial cloud with that of a typical HPC system, and we analyze the various costs associated with running those workflows in the cloud. We find that the performance of clouds is not unreasonable given the hardware resources provided, and that performance comparable to HPC systems can be achieved given similar resources. We also find that the cost of running workflows on a commercial cloud can be reduced by storing data in the cloud rather than transferring it from outside