Statistical analysis of decentralized MUSIC

For large-array processing problems there is a need for decentralized methods that are computationally efficient. A decentralized variant of the MUSIC algorithm, proposed in the literature, is here analysed from a statistical viewpoint, assuming that a large number of snapshots is available. As intuitively expected, the centralized MUSIC algorithm is more accurate than both the local and decentralized versions of MUSIC. More surprisingly, the decentralized variant of MUSIC is not always more accurate than the local MUSIC estimates. The theoretical analysis is supported by numerical examples.The work of Petre Stoica has been supported in part by grants from the Swedish Institute, the Royal Swedish Academy of Engineering Sciences, and the Swedish Research Council for Engineering Sciences.     

Electron microscopy and immunolabeling of Yersinia antigens in human synovial fluid cells

Recent findings have emphasized the involvement of bacterial antigens in synovitis in reactive arthritis. It is still unclear, however, in what form the microbial material exists in the joint. Both antigen-containing cells and intact bacteria have been proposed as candidates on the basis of immunohistochemical studies of the synovial membrane. This study addresses that question by electron microscopy and peroxidase immunolabeling of synovial fluid cells from three patients with reactive arthritis triggered by Yersinia enterocolitica O:3. For all three patients a diffuse reaction in the cytoplasm of phagocytes was interpreted as bacterial material in a degraded form. These results are consistent with our proposal that intact bacteria rarely, if ever, enter the joints of Yersinia-triggered reactive arthritis patients.     

Test of pole-zero cancellation in estimated models

A common problem in examination of identified models is how to test possible pole-zero cancellations. A systematic way of performing such tests taking the uncertainty of the model parameters into account is suggested. In particular, application to models obtained with least squares identification is considered. The proposed method turns out to be an efficient way of applying the generalized least squares method.     

Incorporation of (3H)uridine by the chromatoid body during rat spermatogenesis

The in vitro incorporation of tritiated uridine into RNA by the spermatogenic cells of the rat has been analyzed by high-resolution autoradiography. Special attention has been focused on the unique cytoplasmic organelle, the chromatoid body. After a short labeling time (2 h), this organelle remains unlabeled in the vast majority of the early spermatids although the nuclei are labeled. When the 2-h incubation with (3H)uridine is followed by a 14-h chase, the chromatoid body is seen distinctly labeled in all spermatids during early spermiogenesis from step 1 to step 8. Very few grains are seen elsewhere in the cytoplasm of these cells. When RNA synthesis in the spermatid ceases, the chromatoid body also remains unlabeled. It is likely that the chromatoid body contains RNA which is synthesized in the nuclei of the spermatids. The function of this RNA as a stable messenger RNA needed for the regulation of late spermiogenesis is discussed.     

Can errors-in-variables systems be identified from closed-loop experiments?

Errors-in-variables (EIV) systems are known to be identifiable not generally, but under some specific conditions. These conditions are normally formulated for open-loop systems. This paper examines to what extent an EIV system can be identifiable from closed-loop experiments.     

Use of an electronic tongue to analyze mold growth in liquid media

The feasibility of employing an electronic tongue to measure the growth of mold in a liquid medium was studied. We used the electronic tongue developed at Link?ping University, which is based on pulsed voltammetry and consists of an array of different metal electrodes. Instead of focusing on a single parameter, this device provides information about the condition or quality of a sample or process. Accordingly, the data obtained are complex, and multivariate methods such as principal component analysis (PCA) or projection to latent structures (PLS) are required to extract relevant information. A gas chromatographic technique was developed to measure ergosterol content in mold biomass and was subsequently used as a reference method to investigate the ability of the electronic tongue to measure the growth of mold in liquid media. The result shows that the electronic tongue can monitor mold growth in liquids. In PLS analysis, the electronic tongue signals correlate well with the amount of ergosterol in the mold biomass as well as the microbially induced changes in the pH of the medium.     

Reduced order models for a two-dimensional heat diffusion system

In this paper, a two-dimensional heat diffusion system modelled by a partial differential equation (PDE) is considered. Finite order approximations are constructed first by a direct application of the standard finite difference approximation (FD) scheme. Using standard tools, the constructed FD approximate models are reduced to computationally simpler models. Further, alternative approximate models are proposed using the asymptotic limits of the FD approximations. Numerical experiments suggest that the proposed alternative approximations are more accurate than the FD approximation.     

Eigenvalue location of certain matrices arising in convergence analysis problems

We give simple formulas for the eigenvalues of a certain type of matrices occurring in some convergence analysis problems. Application of the result to a pseudo-linear regression algorithm gives explicit necessary and sufficient conditions for local convergence.