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Several algorithms are presented for the J-spectral factorization of a para-Hermitian polynomial matrix. The four algorithms that are discussed are based on diagonalization, successive factor extraction, interpolation, and the solution of an algebraic Riccati equation, respectively. The paper includes a special algorithm for the factorization of unimodular para-Hermitian polynomial matrices and deals with canonical, noncanonical, and nearly noncanonical factorizations. >

SETTING: Surveillance data from the National Tuberculosis Register for the period 1993-1997 complemented with DNA fingerprinting results of Mycobacterium tuberculosis isolates. OBJECTIVE: To estimate the proportion of disease attributable to recent re-infection among Dutch tuberculosis patients with reported tuberculosis infection or disease before 1981. DESIGN: Data from 1,547 Dutch patients diagnosed between 1994 and 1997 in the Netherlands were studied. Cases with reported tuberculosis infection or disease before 1981 were attributed to reactivation if their M. tuberculosis isolate was unclustered based on DNA fingerprinting or if they were the first case in a cluster, and to re-infection if they were clustered, but not as the first case. RESULTS: In total, 183 Dutch tuberculosis patients (12%) had reported tuberculosis infection or disease before 1981. Tuberculosis in 29 of these patients (16%) was attributed to recent re-infection. CONCLUSION: In this setting with a low tuberculosis incidence, approximately one in six new disease episodes among patients with previous tuberculosis infection or disease may be attributable to recent re-infection

The Netherlands, May 1994 to May 1996. 1) To estimate to what extent drug-resistant tuberculosis was acquired or recently transmitted in The Netherlands, 2) to assess the relevance of drug resistance data as routinely collected, and 3) to describe case management. Prospective descriptive study. Patients diagnosed with drug-resistant tuberculosis were interviewed. Information on patient management and contact tracing was collected. IS6110 restriction fragment length polymorphism (RFLP) patterns of all strains were compared with those of the National RFLP library and clusters were analyzed. In total 193 cases were included in the study. Acquired drug resistance (ADR) was rare. Dutch ADR patients reported receiving treatment a long time previously (mean age 58, mean treatment interval 23 years). Most foreign ADR patients had been treated recently in their country of origin. Of 151 primary drug-resistant (PDR) cases, 129 (85%) were foreign-born, of whom few (8%-19%) had been infected in The Netherlands. Few Dutch PDR cases had been infected recently (mean age 49 years). Rifampicin resistance was more frequently observed in foreign ADR cases than in foreign PDR cases (28% vs 5%; P < 0.001). One third of cases had not been treated according to treatment guidelines. Only a small proportion of drug-resistant cases resulted from recent infection or treatment in The Netherlands. General rates of ADR and PDR do not reflect current Dutch programme performance. For programme monitoring, ADR/PDR rates and their trends must be reported and evaluated in Dutch and foreign patients separately

The problem of J-spectral factorization of polynomial matrices is studied. Existence and uniqueness are discussed, and the differences from the standard case are pointed out. Two first algorithms are proposed for a numerical solution. The first algorithm, which is based on the generalized symmetric factor extraction, features simplicity and is easy to implement via MATLAB. The second algorithm, which is based on diagonalization, applies to a more general class of matrices (including those with zeros on the imaginary axis)