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Fluctuation Analysis (fluctuation + analysis)
Selected AbstractsFluctuation analysis and accuracy of a large-scale in silico screenJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2004H. Merlitz Abstract Using a cascadic version of the stochastic tunneling method we perform an all-atom database screen over 186,000 flexible ligands of the NCI 3D database against the thymidine kinase receptor. By analyzing the errors in the binding energy we demonstrate how the cascadic technique is superior to conventional sequential docking techniques and how reliable results for the determination of the top-scoring ligands could be achieved. The substrate corresponding to the crystal structure used in the screen ranks in the upper 0.05% of the database, validating both docking methodology and the applicability of the scoring function to this substrate. Several high ranking ligands of the database display significant structural similarity with known substrates. A detailed analysis of the accuracy of the screening method is carried out, and its dependence on the flexibility of the ligand is quantified. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1568,1575, 2004 [source] Multifractal detrended fluctuation analysis of streamflow series of the Yangtze River basin, ChinaHYDROLOGICAL PROCESSES, Issue 26 2008Qiang Zhang Abstract Scaling and multifractal properties of the hydrological processes of the Yangtze River basin were explored by using a multifractal detrended fluctuation analysis (MF-DFA) technique. Long daily mean streamflow series from Cuntan, Yichang, Hankou and Datong stations were analyzed. Using shuffled streamflow series, the types of multifractality of streamflow series was also studied. The results indicate that the discharge series of the Yangtze River basin are non-stationary. Different correlation properties were identified within streamflow series of the upper, the middle and the lower Yangtze River basin. The discharge series of the upper Yangtze River basin are characterized by short memory or anti-persistence; while the streamflow series of the lower Yangtze River basin is characterized by long memory or persistence. h(q) vs q curves indicate multifractality of the hydrological processes of the Yangtze River basin. h(q) curves of shuffled streamflow series suggest that the multifractality of the streamflow series is mainly due to the correlation properties within the hydrological series. This study may be of practical and scientific importance in regional flood frequency analysis and water resource management in different parts of the Yangtze River basin. Copyright © 2008 John Wiley & Sons, Ltd. [source] Long-term memory of the hydrological cycle and river runoffs in China in a high-resolution climate modelINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2006Richard Blender Abstract The hydrological cycle in China is analysed on the basis of a 250-years present-day climate simulation with a high-resolution (T63, ,2° × 2° ) coupled atmosphere-ocean circulation model (ECHAM5/MPI-OM). The analysis of the annual data in the model simulation reveals long-term memory (LTM) on decadal time scales in some components of the hydrological cycle. LTM is characterised by a scaling exponent , > 0 in the power spectrum S(f) , f,, for low frequencies f and is determined by detrended fluctuation analysis (DFA). The simulated annual precipitation and atmospheric near-surface temperature fields show, as in the observations, a white low-frequency spectrum and, hence, no long-term memory in East Asia. However, simulated river flows of the Yangtze and the Huang He reveal LTM with scaling exponents , = 0.3,0.4 (similar to the observations and that of the river Nile) extending beyond the decadal time scale. The model soil temperature indicates restricted memory up to time scales of approximately 30 years. In addition, the model's soil wetness, evaporation, and local runoff show memory on this time scale in a zonal belt at the latitude of Mongolia. Copyright © 2006 Royal Meteorological Society. [source] Kinetics of both synchronous and asynchronous quantal release during trains of action potential-evoked EPSCs at the rat calyx of HeldTHE JOURNAL OF PHYSIOLOGY, Issue 2 2007V. Scheuss We studied the kinetics of transmitter release during trains of action potential (AP)-evoked excitatory postsynaptic currents (EPSCs) at the calyx of Held synapse of juvenile rats. Using a new quantitative method based on a combination of ensemble fluctuation analysis and deconvolution, we were able to analyse mean quantal size (q) and release rate (,) continuously in a time-resolved manner. Estimates derived this way agreed well with values of q and quantal content (M) calculated for each EPSC within the train from ensemble means of peak amplitudes and their variances. Separate analysis of synchronous and asynchronous quantal release during long stimulus trains (200 ms, 100 Hz) revealed that the latter component was highly variable among different synapses but it was unequivocally identified in 18 out of 37 synapses analysed. Peak rates of asynchronous release ranged from 0.2 to 15.2 vesicles ms,1 (ves ms,1) with a mean of 2.3 ± 0.6 ves ms,1. On average, asynchronous release accounted for less than 14% of the total number of about 3670 ± 350 vesicles released during 200 ms trains. Following such trains, asynchronous release decayed with several time constants, the fastest one being in the order of 15 ms. The short duration of asynchronous release at the calyx of Held synapse may aid in generating brief postsynaptic depolarizations, avoiding temporal summation and preserving action potential timing during high frequency bursts. [source] Fluorescence correlation spectroscopy for the detection and study of single molecules in biologyBIOESSAYS, Issue 8 2002Miguel Ángel Medina The recent development of single molecule detection techniques has opened new horizons for the study of individual macromolecules under physiological conditions. Conformational subpopulations, internal dynamics and activity of single biomolecules, parameters that have so far been hidden in large ensemble averages, are now being unveiled. Herein, we review a particular attractive solution-based single molecule technique, fluorescence correlation spectroscopy (FCS). This time-averaging fluctuation analysis which is usually performed in Confocal setups combines maximum sensitivity with high statistical confidence. FCS has proven to be a very versatile and powerful tool for detection and temporal investigation of biomolecules at ultralow concentrations on surfaces, in solution, and in living cells. The introduction of dual-color cross-correlation and two-photon excitation in FCS experiments is currently increasing the number of promising applications of FCS to biological research. BioEssays 24:758,764, 2002. © 2002 Wiley Periodicals, Inc. [source] | ||||||||||