排序方式: 共有52条查询结果,搜索用时 31 毫秒
1.
Resolution and uniqueness of estimated parameters of a model of thin filament regulation in solution
Srboljub M. Mijailovich Xiaochuan Li Juan C. del Álamo R. Hugh Griffiths Vojislav Kecman Michael A. Geeves 《Computational Biology and Chemistry》2010,34(1):19-33
The estimation of chemical kinetic rate constants for any non-trivial model is complex due to the nonlinear effects of second order chemical reactions. We developed an algorithm to accomplish this goal based on the Damped Least Squares (DLS) inversion method and then tested the effectiveness of this method on the McKillop–Geeves (MG) model of thin filament regulation. The kinetics of MG model is defined by a set of nonlinear ordinary differential equations (ODEs) that predict the evolution of troponin–tropomyosin–actin and actin–myosin states. The values of the rate constants are estimated by integrating these ODEs numerically and fitting them to a series of stopped-flow pyrene fluorescence transients of myosin-S1 fragment binding to regulated actin in solution. The accuracy and robustness of the estimated rate constants are evaluated for DLS and two other methods, namely quasi-Newton (QN) and simulated annealing (SA). The comparison of these methods revealed that SA provides the best estimates of the model parameters because of its global optimization scheme. However it converges slowly and does quantify the uniqueness of the estimated parameters. On the other hand the QN method converges rapidly but only if the initial guess of the parameters is close to the optimum values, otherwise it diverges. Overall, the DLS method proves to be the most convenient method. It converges fast and was able to provide excellent estimates of kinetic parameters. Furthermore, DLS provides the model resolution matrix, which quantifies the interdependence of model parameters thereby evaluating the uniqueness of their estimated values. This property is essential for estimating of the dependence of the model parameters on experimental conditions (e.g. Ca2+ concentration) when it is assessed from noisy experimental data such as pyrene fluorescence from stopped-flow transients. The advantages of the DLS method observed in this study should be further examined in other physicochemical systems to firmly establish the observed effectiveness of DSL vs. the other parameter estimation methods. 相似文献
2.
Vojislav Spasojevic Ana Mrakovic Marija Perovic Vladan Kusigerski Jovan Blanusa 《Journal of nanoparticle research》2011,13(2):763-771
Single-phase perovskite compound La0.7Ca0.3MnO3 was synthesised by a high-energy ball milling in a single step processing. Structure and morphology characterizations revealed
nanoparticle nature of this mixed valent manganite with the average particle diameter of 9 nm. Comprehensive set of magnetic
measurements showed that the system can be described as an ensemble of interacting magnetic nanoparticles where each particle
possesses high magnetic moment, i.e., superspin. Furthermore, magnetic behavior showed contributions from both superspin-glass
(SSG) and superparamagnetic (SP) states, and the prevailing properties depended on the experimental conditions. It was established
that SSG state dominated in low magnetic fields up to 500 Oe while in higher applied fields suppression of collective behavior
occurred and individual characteristics of nanoparticles prevailed. It was also concluded that the applied method of synthesis
produced system with high magnetic anisotropy as well as with the large nanoparticle shell whose thickness amounts 30% of
a particle diameter. 相似文献
3.
Vojislav G. Avakumović 《Mathematische Zeitschrift》1942,47(1):141-152
Ohne Zusammenfassung 相似文献
4.
5.
6.
Mun BS Watanabe M Rossi M Stamenkovic V Markovic NM Ross PN 《The Journal of chemical physics》2005,123(20):204717
The surface valence-band densities of states (DOS) of Pt(3)M (M=Ti,V,Cr,Fe,Co,Ni) polycrystalline alloys were investigated with ultraviolet photoemission spectroscopy. Upon annealing the ion-sputter-cleaned alloys at high temperatures, the observed valence-band DOS spectra clearly show the modified electronic structures on the surfaces suggesting the surface segregation of Pt as predicted in thermodynamic models. The measured d-band centers and widths for the annealed alloy surfaces show qualitatively the same trend as predicted by density-functional-theory calculations based on the model of a Pt "skin" on the topmost surface layer and a subsurface layer enriched in the 3d transition metal. 相似文献
7.
Samaržija-Jovanović Suzana Jovanović Vojislav Jovanović Tijana Petković Branka Marković Gordana Porobić Slavica Marinović-Cincović Milena 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12467-12479
Journal of Thermal Analysis and Calorimetry - This work investigated the thermal characteristics of irradiated composite materials formulated on the urea–formaldehyde resin (UF) and... 相似文献
8.
Kenji Mizoguchi Tetsushi Takanashi Hirokazu Sakamoto Ljiljana Damjanovic Vojislav I. Srdanov 《Molecular Crystals and Liquid Crystals》2013,570(2):467-472
Abstract Pressure (0–19 kbar) and temperature (4–300 K) dependent EPR study of Sodium-Electro-Sodalite (SES) is presented. SES, which consists of a bcc sub-lattice of F-centers supported by a zeolite-like framework, is known to be a Mott insulator at room temperature. On cooling, SES undergoes an AF transition at 48±2 K providing the first example of an s-electron antiferromagnet. We find that the width of the EPR resonance above T N is influenced not only by a strong exchange interaction, but also by a fast spin-lattice relaxation. Also, with increasing pressure, T N decreases linearly and extrapolates to 0 K at about 65 kbar. The reason for this seemingly unexpected behavior is briefly discussed. 相似文献
9.
10.
Vojislav Petrovi 《Journal of Graph Theory》1988,12(3):317-325
Let H(n, i) be a simple (n ? 1)-path v1 → v2 → …? → vn with an additional arc v1vi (3 ? i ? n). We prove that for each n and i (3 ? i ? n), with few exceptions, every n-tournament Tn contains a copy of H(n, i). 相似文献