Scaling Properties of Paths on Graphs

Let $G$ be a directed graph on finitely many vertices and edges, and assign a positive weight to each edge on $G$. Fix vertices $u$ and $v$ and consider the set of paths that start at $u$ and end at $v$, self-intersecting in any number of places along the way. For each path, sum the weights of its edges, and then list the path weights in increasing order. The asymptotic behaviour of this sequence is described, in terms of the structure and type of strongly connected components on the graph. As a special case, for a Markov chain the asymptotic probability of paths obeys either a power law scaling or a weaker type of scaling, depending on the structure of the transition matrix. This generalizes previous work by Mandelbrot and others, who established asymptotic power law scaling for special classes of Markov chains.Comment: 23 pages, 2 figure

The supersymmetric Penrose transform in six dimensions

We give a supersymmetric extension to the six-dimensional Penrose transform and give an integral formula for the on-shell (0, 2) supermultiplet. The relationship between super fields on space-time and twistor space is clarified and the space-time superfield constraint equations are derived from the geometry of supertwistor space. We also explain the extension to more general (0,n) supermultiplets and give twistor actions for these theories.Comment: 20 page

Working with OpenCL to Speed Up a Genetic Programming Financial Forecasting Algorithm: Initial Results

The genetic programming tool EDDIE has been shown to be a successful financial forecasting tool, however it has suffered from an increase in execution time as new features have been added. Speed is an important aspect in financial problems, especially in the field of algorithmic trading, where a delay in taking a decision could cost millions. To offset this performance loss, EDDIE has been modified to take advantage of multi-core CPUs and dedicated GPUs. This has been achieved by modifying the candidate solution evaluation to use an OpenCL kernel, allowing the parallel evaluation of solutions. Our computational results have shown improvements in the running time of EDDIE when the evaluation was delegated to the OpenCL kernel running on a multi-core CPU, with speed ups up to 21 times faster than the original EDDIE algorithm. While most previous works in the literature reported significantly improvements in performance when running an OpenCL kernel on a GPU device, we did not observe this in our results. Further investigation revealed that memory copying overheads and branching code in the kernel are potentially causes of the (under-)performance of the OpenCL kernel when running on the GPU device

Galaxy population properties in the rich clusters MS0839.8+2938, 1224.7+2007 and 1231.3+1542

This paper discusses the galaxy populations of three rich clusters, with redshift 0.19 (0839+29), 0.24 (1231+15), and 0.32 (1224+20), from the database of the CNOC1 consortium. The data consist of spectra of 52 cluster members for 0839+29, 30 members for 1224+15, and 82 members for 1231+15, and there are comparable numbers of field galaxy spectra. 0839+29 is compact with no strong radial gradients, and possibly dusty. 1224+20 is isolated in redshift, has low velocity dispersion around the cD galaxy, and low 4000A break. 1231+15 is asymmetrical and we discuss the possibility that it may be a recent merger of two old clusters. We find few galaxies in 0839+29 and 1231+15 with ongoing or recently truncated star-formation.Comment: 16 pages and 20 diagrams, to appear in A

Muon and neutrino fluxes

The result of a new calculation of the atmospheric muon and neutrino fluxes and the energy spectrum of muon-neutrinos produced in individual extensive air showers (EAS) initiated by proton and gamma-ray primaries is reported. Also explained is the possibility of detecting atmospheric nu sub mu's due to gamma-rays from these sources

Airfoil shape and thickness effects on transonic airloads and flutter

A transient pulse technique is used to obtain harmonic forces from a time-marching solution of the complete unsteady transonic small perturbation potential equation. The unsteady pressures and forces acting on a model of the NACA 64A010 conventional airfoil and the MBB A-3 supercritical airfoil over a range of Mach numbers are examined in detail. Flutter calculations at constant angle of attack show a similar flutter behavior for both airfoils, except for a boundary shift in Mach number associated with corresponding Mach number shift in the unsteady aerodynamic forces. Differences in the static aeroelastic twist behavior for the two airfoils are significant

The muon content of gamma-ray showers

The result of a calculation of the expected number of muons in gamma ray initiated and cosmic ray initiated air showers using a realistic model of hadronic collisions in an effort to understand the available experimental results and to assess the feasibility of using the muon content of showers as a veto to reject cosmic ray initiated showers in ultra-high energy gamma ray astronomy are reported. The possibility of observing very-high energy gamma-ray sources by detecting narrow angle anisotropies in the high energy muon background radiation are considered

The relationship between angiogenesis and cyclooxygenase-2 expression in prostate cancer

<b>OBJECTIVE</b>: To test the hypothesis that angiogenesis in prostate cancer is associated with tumour invasion and metastasis, and that this is mediated through increased cyclooxygenase-2 (COX-2) expression. <b>PATIENTS AND METHODS</b>: Angiogenesis was assessed in 105 patients with either prostate cancer (79) or benign prostatic hyperplasia (BPH, 26) and these data correlated with levels of COX-2 expression in the same dataset. The mean microvessel density (MVD) was analysed as a marker of angiogenesis, using the endothelial antigen CD34 stained by immunohistochemistry. <b>RESULTS</b>: There was no difference in MVD in progressive tumour stages compared with BPH. There was a negative correlation between MVD and COX-2 expression, but the effect of increased COX-2 expression on MVD was not marked. <b>CONCLUSION</b>: These data suggest that COX-2 drives tumour spread in prostate cancer by means other than the promotion of angiogenesis

Transonic stability and control characteristics of a 0.015 scale model 69-0 of the space shuttle orbiter with forebody RSI modification in the NASA/LaRC 8 foot TPT (LA72)

Tests were conducted in the NASA/LaRC 8 foot transonic wind tunnel from March 26 through 31, 1976. The model was a 0.015 scale SSV Orbiter with forebody modifications to simulate slight reductions in the reusable surface insulation (RSI) thickness. Six component aerodynamic force and moment data were obtained at Mach numbers from 0.35 to 1.20 over an angle of attack range from -2 deg to 20 deg at sideslip angles of 0 deg and 5 deg

Parallel density matrix propagation in spin dynamics simulations

Several methods for density matrix propagation in distributed computing environments, such as clusters and graphics processing units, are proposed and evaluated. It is demonstrated that the large communication overhead associated with each propagation step (two-sided multiplication of the density matrix by an exponential propagator and its conjugate) may be avoided and the simulation recast in a form that requires virtually no inter-thread communication. Good scaling is demonstrated on a 128-core (16 nodes, 8 cores each) cluster.Comment: Submitted for publicatio