Biomedical subjects

Fanbo Meng

Publications and source records attributed to Fanbo Meng.

4 recordsLinked to original sources

PubMed2006

A comparison between photon counting histogram and fluorescence intensity distribution analysis.

Photon counting histogram (PCH) and fluorescence intensity distribution analysis (FIDA) are two methods that were developed independently but reported almost simultaneously. Both of them have been successfully applied to fluorescence fluctuation spectroscopy (FFS). Though publications have indicated that they are theoretically equivalent, they are still commonly considered as different methods, especially in their ways to treat the point spread functions (PSFs). In this paper, the two methods are examined in detail for a direct comparison. After a direct proof of the theoretical equivalence, the authors further point out that PCH and FIDA are completely equivalent in the way of modeling PSFs; that is, any modeling approach developed from one of them can always be applied to the other. It is also demonstrated that simplified FIDA and PCH formulas in the form of power series can be applied for fast and precise numerical calculations. The two methods are also compared for their merits in the calculation efficiency.

Journal Article↗

PubMed2006

Extended photon counting histogram and fluorescence intensity distribution analysis approaches for optically biased photon counting statistics.

A gradient potential induced by a strongly focused laser beam can perturb the diffusion dynamics of particles in solutions and result in biased photon counting statistics in fluorescence fluctuation spectroscopy (FFS). In this paper, the theories of the photon counting histogram (PCH) and fluorescence intensity distribution analysis (FIDA) approaches are extended independently to fit the biased experimental data and retrieve the unbiased parameters, i.e., the average number of the sample particles in the focal volume N, their brightness epsilon, and polarizability alpha. The extended theories are tested using Monte Carlo simulations for single- and double-component systems. It is also proved numerically and analytically that the extended PCH and FIDA approaches are completely equivalent. Practical implementations and possible applications of extended PCH and FIDA are discussed.

Journal Article↗

PubMed2005

Fluorescence correlation spectroscopy analysis of diffusion in a laser gradient field: a numerical approach.

Fluorescence correlation spectroscopy (FCS) is widely used in biological systems. When the laser is intense enough, such as in two-photon experiments, the trapping force due to the laser gradient field can change the diffusion behavior of the fluorescent particles and induce error in the FCS measurements. Previous studies on biased FCS are qualitative. In this article, a numerical approach is proposed to treat the problem quantitatively. By assumption of a "spherical symmetry", biased FCS curves can be calculated numerically and fitted to the experimental data to retrieve the unbiased particle number, diffusion time, and polarizability of the fluorescent particles as well as the strength of the gradient field. It has been proven using simulated FCS data that the discrepancy caused by the spherical symmetry approximation is independent of the gradient field strength; therefore it can be eliminated by a calibration.

Journal Article↗

PubMed2003

Beta-blockers are effective in congestive heart failure patients with atrial fibrillation.

BACKGROUND: It is controversial whether or not beta-blockers are effective in patients with congestive heart failure (CHF) who are complicated by persistent atrial fibrillation (AF). METHODS: We attempted to determine the potential differences in the efficacy between atrial fibrillation and sinus rhythm in 70 CHF patients with NYHA class II-IV and radionuclide ejection fraction (LVEF) <40% who received metoprolol or carvedilol over 16 weeks. RESULTS: Left ventricular end-diastolic dimension was decreased in AF group (n=24) 4 weeks (early) and 16 to 48 weeks (late) after introduction of beta-blockers (P<.05, P<.001), but not in the sinus rhythm (NSR) group (n=46). End-systolic dimension was decreased in both the AF group (P<.01, P<.0001) and the NSR group (P<.01, P<.0001). LVEF was increased in both the AF group (P<.0005, P<.0001) and the NSR group (P<.0001, P<.0001) early and late after the therapy. Increase in LVEF by the therapy tended to be higher in the AF group than in the NSR group (P=.056). Plasma brain natriuretic peptide level did not change significantly throughout the observation period, although the level tended to be lowered in the AF group late after introduction of beta-blockers (P=.093). CONCLUSIONS: Because beta-blockers are effective in both NSR and AF patients with CHF, such a mode of therapy should be recommended in patients with AF.

Adrenergic beta-Antagonists↗