Sensitivity of the stationary distribution vector for an ergodic Markov chain

AbstractStationary distribution vectors p∞ for Markov chains with associated transition matrices T are important in the analysis of many models in the mathematical sciences, such as queuing networks, input-output economic models, and compartmental tracer analysis models. The purpose of this paper is to provide insight into the sensitivity of p∞ to perturbations in the transition probabilities of T and to understand some of the difficulties in computing an accurate p∞. The group inverse A# of I − T is shown to be of fundamental importance in understanding sensitivity or conditioning of p∞. The main result shows that if there is a state that is accessible from every other state and the corresponding column of T has no small off-diagonal elements, then p∞ cannot be sensitive to small perturbations in T. Ecological examples are given. A new algorithm for calculating A# is described

Spin Correlation Coefficients in pp-->pnpi+ from 325 to 400 MeV

The spin correlation coefficient combinations Axx + Ayy, Axx - Ayy and the analyzing powers Ay(theta) were measured for pp-->pnpi+ at beam energies of 325, 350, 375 and 400 MeV. A polarized internal atomic hydrogen target and a stored, polarized proton beam were used. These polarization observables are sensitive to contributions of higher partial waves. A comparison with recent theoretical calculations is provided.Comment: 8 Pages, 1 Table, 5 Figures. Accepted for publication in Phys. Lett.

Boosting parallel perceptrons for label noise reduction in classification problems

The final publication is available at Springer via http://dx.doi.org/10.1007/11499305_60Proceedings of First International Work-Conference on the Interplay Between Natural and Artificial Computation, IWINAC 2005, Las Palmas, Canary Islands, Spain, June 15-18, 2005Boosting combines an ensemble of weak learners to construct a new weighted classifier that is often more accurate than any of its components. The construction of such learners, whose training sets depend on the performance of the previous members of the ensemble, is carried out by successively focusing on those patterns harder to classify. This fact deteriorates boosting’s results when dealing with malicious noise as, for instance, mislabeled training examples. In order to detect and avoid those noisy examples during the learning process, we propose the use of Parallel Perceptrons. Among other things, these novel machines allow to naturally define margins for hidden unit activations. We shall use these margins to detect which patterns may have an incorrect label and also which are safe, in the sense of being well represented in the training sample by many other similar patterns. As candidates for being noisy examples we shall reduce the weights of the former ones, and as a support for the overall detection procedure we shall augment the weights of the latter ones.With partial support of Spain’s CICyT, TIC 01–572, TIN 2004–0767

Studies of Proton Induced Neutral Pion Production Near Threshold

Supported by the National Science Foundation and Indiana Universit

Initial singlet and triplet spin state contributions to pp -> pp pi0

The PINTEX facility at the IUCF Cooler ring, dedicated to the study of spin dependence in nucleon-nucleon interactions, has been used to measure polarization observables of the reaction pp -> pp pi0 at beam energies between 325 and 400 MeV. The stored polarized proton beam had spin projections both in the longitudinal and the transverse directions with respect to the beam momentum. We report here on the measurements of the relative transverse and longitudinal spin-dependent cross sections, deltasigma_T/sigma_tot and deltasigma_L/sigma_tot, and how from these observables the initial spin singlet and triplet cross sections are obtained. Considering angular momentum states less or equal to one, the contribution of the Ps partial waves to the cross section can be extracted.Comment: Contribution to PANIC99, XVth Particles and Nuclei International Conference, June 10-16, 1999, Uppsala, Sweden. Latex, 5 pages, 3 figure

Measurement of Charged Pion Yields from Nuclei in (p,Pi+) Reactions Very Near Threshold

This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit

Development of a Pi° Detector System

This work was supported by National Science Foundation Grants PHY 76-84033A01, PHY 78-22774, and Indiana Universit

Improved Method of Neutron Activation Analysis for Microleakage Studies

Improvements in the neutron activation technique for studying microleakage were achieved by selecting more suitable tracers and by using a more accurate method for evaluation of the activation data. Dysprosium was the most suitable tracer; it provided the least variation in the results and allowed the fastest activation and counting procedure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66594/2/10.1177_00220345740530022901.pd

Ab initio study of ferroelectric domain walls in PbTiO3

We have investigated the atomistic structure of the 180-degree and 90-degree domain boundaries in the ferroelectric perovskite compound PbTiO3 using a first-principles ultrasoft-pseudopotential approach. For each case we have computed the position, thickness and creation energy of the domain walls, and an estimate of the barrier height for their motion has been obtained. We find both kinds of domain walls to be very narrow with a similar width of the order of one to two lattice constants. The energy of the 90-dergree domain wall is calculated to be 35 mJ/m^2, about a factor of four lower than the energy of its 180-degree counterpart, and only a miniscule barrier for its motion is found. As a surprising feature we detected a small offset of 0.15-0.2 eV in the electrostatic potential across the 90-degree domain wall.Comment: 12 pages, with 9 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/bm_dw/index.htm

The macrophage response to mycobacterium tuberculosis and opportunities for autophagy inducing nanomedicines for Tuberculosis therapy

The major causative agent of tuberculosis (TB), i.e., Mycobacterium tuberculosis (Mtb), has developed mechanisms to evade host defense responses and persist within host cells for prolonged periods of time. Mtb is also increasingly resistant to existing anti-TB drugs. There is therefore an urgent need to develop new therapeutics for TB and host directed therapies (HDTs) hold potential as effective therapeutics for TB. There is growing interest in the induction of autophagy in Mtb host cells using autophagy inducing compounds (AICs). Nanoparticles (NPs) can enhance the effect of AICs, thus improving stability, enabling cell targeting and providing opportunities for multimodal therapy. In this review, we focus on the macrophage responses to Mtb infection, in particular, the mechanistic aspects of autophagy and the evasion of autophagy by intracellular Mtb. Due to the overlap between the onset of autophagy and apoptosis; we also focus on the relationship between apoptosis and autophagy