Modeling errors in Kalman filters

Suboptimal filters based on erroneous models of system dynamics and on a priori statistic

Singular Vertices in the Strong Coupling Phase of Four-Dimensional Simplicial Gravity

We study four-dimensional simplicial gravity through numerical simulation with special attention to the existence of singular vertices, in the strong coupling phase, that are shared by abnormally large numbers of four-simplices. We attempt to cure this disease by adding a term to the action which suppresses such singular vertices. For a sufficiently large coefficient of the additional term, however, the phase transition disappears and the system is observed to be always in the branched polymer phase for any gravitational constant.Comment: 11 pages, 7 Postscript figure

Relationships between log N-log S and celestial distribution of gamma-ray bursts

The apparent conflict between log N-log S curve and isotropic celestial distribution of the gamma ray bursts is discussed. A possible selection effect due to the time profile of each burst is examined. It is shown that the contradiction is due to this selection effect of the gamma ray bursts

A new phase structure in three-dimensional dynamical triangulation model

We investigate a new phase structure of the three-dimensional dynamical triangulation model with an additional local term by Monte Carlo simulation. We find that the first order phase transition observed for the naive Einstein-Hilbert action terminates at a finite coefficient of the new term. The phase transition turns into second order at the endpoint, beyond which it becomes a crossover.Comment: 3 pages, 3 EPS figures, uses espcrc2, talk presented at "Lattice'97", to appear in the proceeding

Changes in plasma levels of B-type natriuretic peptide with acute exacerbations of chronic obstructive pulmonary disease.

Background: Elevated plasma B-type natriuretic peptide (BNP) levels and their association with heart failure have been reported in subjects with acute exacerbations of chronic obstructive pulmonary disease (AECOPD). Purpose: To examine and compare plasma BNP levels and diastolic and systolic dysfunction in subjects with AECOPD and s table chronic obstructive pulmonary disease (COPD). Methods: In all,87 unselected consecutive hospitalizations due to AECOPD in 61 subjects and a total of 190 consecutive subjects with stable COPD were recruited. Plasma BNP levels were compared cross-sectionally and longitudinally. Transthoracic echocardiographic examinations were also performed in the hospitalized subjects. Results: In the hospitalized subjects, the median plasma BNP level (interquartile range) was 55.4 (26.9–129.3) pg/mL and was higher than that of patients with stable COPD: 18.3 (10.0–45.3)for Global Initiative for Chronic Obstructive Lung Disease grade I; 25.8 (11.0–53.7) for grade II; 22.1 (9.1–52.6) for grade III; and 17.2 (9.6–22.9) pg/mL for grade IV, all P,0.001. In 15 subjects studied prospectively, the median plasma BNP level was 19.4 (9.8–32.2) pg/mL before AECOPD, 72.7 (27.7–146.3) pg/mL during AECOPD, and 14.6 (12.9–39.0) pg/mL after AECOPD (P,0.0033 and P,0.0013, respectively). Median plasma BNP levels during AECOPD were significantly higher in ten unsuccessfully discharged subjects 260.5 (59.4–555.0) than in 48 successfully discharged subjects 48.5(24.2–104.0) pg/mL (P=0.0066). Only 5.6% of AECOPD subjects were associated with systolic dysfunction defined as a left ventricular ejection fraction (LVEF),50%; a further 7.4% were considered to have impaired relaxation defined as an E/A wave velocity ratio,0.8 and a deceleration time of E.240 ms. BNP levels were weakly correlated with the E/peak early diastolic velocity of the mitral annulus (Ea) ratio (Spearman’s rank correlation coefficient =0.353,P =0.018), but they were not correlated with the LVEF (Spearman’s rank correlation coefficient =−0.221,P = 0.108). Conclusion: A modest elevation of plasma BNP is observed during AECOPD. It appears that AECOPD may have an impact on plasma BNP levels that is not attributable to heart failure