16,142 research outputs found
Modeling errors in Kalman filters
Suboptimal filters based on erroneous models of system dynamics and on a priori statistic
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
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
Improved Perturbation Method and its Application to the IIB Matrix Model
We present a new scheme for extracting approximate values in ``the improved
perturbation method'', which is a sort of resummation technique capable of
evaluating a series outside the radius of convergence. We employ the
distribution profile of the series that is weighted by nth-order derivatives
with respect to the artificially introduced parameters. By those weightings the
distribution becomes more sensitive to the ``plateau'' structure in which the
consistency condition of the method is satisfied. The scheme works effectively
even in such cases that the system involves many parameters. We also propose
that this scheme has to be applied to each observables separately and be
analyzed comprehensively.
We apply this scheme to the analysis of the IIB matrix model by the improved
perturbation method obtained up to eighth order of perturbation in the former
works. We consider here the possibility of spontaneous breakdown of Lorentz
symmetry, and evaluate the free energy and the anisotropy of space-time extent.
In the present analysis, we find an SO(10)-symmetric vacuum besides the SO(4)-
and SO(7)-symmetric vacua that have been observed. It is also found that there
are two distinct SO(4)-symmetric vacua that have almost the same value of free
energy but the extent of space-time is different. From the approximate values
of free energy, we conclude that the SO(4)-symmetric vacua are most preferred
among those three types of vacua.Comment: 52 pages, published versio
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