Mark A. Taylor

Nonlinear dynamics of immunogenic tumors: parameter estimation and global bifurcation analysis.

We present a mathematical model of the cytotoxic T lymphocyte response to the growth of an immunogenic tumor. The model exhibits a number of phenomena that are seen in vivo, including immunostimulation of tumor growth, sneaking through of the tumor, and formation of a tumor dormant state. The model is used to describe the kinetics of growth and regression of the B-lymphoma BCL1 in the spleen of mice. By comparing the model with experimental data, numerical estimates of parameters describing processes that cannot be measured in vivo are derived. Local and global bifurcations are calculated for realistic values of the parameters. For a large set of parameters we predict that the course of tumor growth and its clinical manifestation have a recurrent profile with a 3- to 4-month cycle, similar to patterns seen in certain leukemias.

An Algorithm for Computing Fekete Points in the Triangle

On the line and its tensor products, Fekete points are known to be the Gauss--Lobatto quadrature points. But unlike high-order quadrature, Fekete points generalize to non-tensor-product domains such as the triangle. Thus Fekete points might serve as an alternative to the Gauss--Lobatto points for certain applications. In this work we present a new algorithm to compute Fekete points and give results up to degree 19 for the triangle. For degree d > 10 these points have the smallest Lebesgue constant currently known. The computations validate a conjecture of Bos [ J. Approx. Theory, 64 (1991), pp. 271--280] that Fekete points along the boundary of the triangle are the one-dimensional Gauss--Lobatto points.

Architecture of LA-MPI, a network-fault-tolerant MPI

Summary form only given. We discuss the unique architectural elements of the Los Alamos message passing interface (LA-MPI), a high-performance, network-fault-tolerant, thread-safe MPI library. LA-MPI is designed for use on terascale clusters which are inherently unreliable due to their sheer number of system components and trade-offs between cost and performance. We examine in detail the design concepts used to implement LA-MPI. These include reliability features, such as application-level checksumming, message retransmission, and automatic message rerouting. Other key performance enhancing features, such as concurrent message routing over multiple, diverse network adapters and protocols, and communication-specific optimizations (e.g., shared memory) are examined.

Tensor product Gauss-Lobatto points are Fekete points for the cube

Tensor products of Gauss-Lobatto quadrature points are frequently used as collocation points in spectral element methods. Unfortunately, it is not known if Gauss-Lobatto points exist in non-tensor-product domains like the simplex. In this work, we show that the n-dimensional tensor-product of Gauss-Lobatto quadrature points are also Fekete points. This suggests a way to generalize spectral methods based on Gauss-Lobatto points to non-tensor-product domains, since Fekete points are known to exist and have been computed in the triangle and tetrahedron. In one dimension this result was proved by Fejer in 1932, but the extension to higher dimensions in non-trivial.

ANOMALOUS SCALING OF LOW-ORDER STRUCTURE FUNCTIONS OF TURBULENT VELOCITY

It is now believed that the scaling exponents of moments of velocity increments are anomalous, or that the departures from Kolmogorovs (1941) self-similar scaling increase nonlinearly with the increasing order of the moment. This appears to be true whether one considers velocity increments themselves or their absolute values. However, moments of order lower than 2 of the absolute values of velocity increments have not been investigated thoroughly for anomaly. Here, we discuss the importance of the scaling of non-integer moments of order between +2 and

The Couette configuration of the Los Alamos Neutron Science Center Neutron Rheometer for the investigation of polymers in the bulk via small-angle neutron scattering

-1

Isotropic third-order statistics in turbulence with helicity: the 2/15-law

, and obtain them from direct numerical simulations at moderate Taylor microscale Reynolds numbers

Network Fault Tolerance in LA-MPI

R_lambdale

Comparison of regularizations of vortex sheet motion

450, and experimental data at high Reynolds numbers

Global and Regional Atmospheric Modeling Using Spectral Elements

(R_lambda approx 10,000)