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1.
Delayed feedbacks are quite common in many physical and biological systems and in particular many physiological systems. Delay
can cause a stable system to become unstable and vice versa. One of the well-studied non-biological chemical oscillators is
the Belousov-Zhabotinskii (BZ) reaction. This gives relaxation oscillations for a considerable period of time under batch
conditions. This paper deals with the effect of perturbing the limit cycle oscillation of BZ reaction by employing a delayed
electrical feedback to the system under batch conditions. The parameters chosen to study are external resistance and delay.
For various resistances and delays the system was electrically perturbed and found to exhibit various complex mixed mode oscillations.
The dynamic features are accounted for by the Oregonator model, with time delay incorporated in one of the variables.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Sharma K Police A Kumar A Pawar GV Giri S Rajagopal S Mullangi R 《Biomedical chromatography : BMC》2012,26(7):833-838
A highly sensitive, rapid assay method was developed and validated for the estimation of lorglumide in mouse plasma using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in positive‐ion mode. The assay procedure involves extraction of lorglumide and phenacetin (internal standard, IS) from mouse plasma with simple protein precipitation. Chromatographic separation was achieved using an isocratic mobile (0.2% formic acid solution–acetonitrile, 20:80, v/v) at a flow‐rate of 0.5 mL/min on an Atlantis dC18 column maintained at 40 °C with a total run time of 4.0 min. The MS/MS ion transitions monitored were 459.2 → 158.4 for lorglumide and 180.1 → 110.1 for IS. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.42 ng/mL and the linearity range extended from 0.42 to 500 ng/mL. The intra‐ and inter‐day precisions were in the ranges of 1.47–10.9 and 3.56–7.53, respectively. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
6.
G. Venkataramana Reddy R. Chandraganthi K. Vasanthi R. Sriram 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1997-2015
Abstract Polymerizations of methyl methacrylate (MMA) and acrylonitrile (AN) were carried out in aqueous nitric acid at 30°C with the redox initiator system ammonium ceric nitrate-ethyl cellosolve (EC). A short induction period was observed as well as the attainment of a limiting conversion for polymerization reactions. The consumption of ceric ion was first order with respect to Ce(IV) concentration in the concentration range (0.2–0.4) × 10?2 M, and the points at higher and lower concentrations show deviations from a linear fit. The plots of the inverse of pseudo-first-order rate constant for ceric ion consumption, (k 1)?1 vs [EC]?1, gave straight lines for both the monomer systems with nonzero intercepts supporting complex formation between Ce(IV) and EC. The rate of polymerization increases regularly with [Ce(IV)] up to 0.003 M, yielding an order of 0.41, then falls to 0.0055 M and again shows a rise at 0.00645 M for MMA polymerization. For AN polymerization, R p shows a steep rise with [Ce(IV)] up to 0.001 M, and beyond this concentration R p shows a regular increase with [Ce(IV)], yielding an order of 0.48. In the presence of constant [NO? 3], MMA and AN polymerizations yield orders of 0.36 and 0.58 for [Ce(IV)] variation, respectively. The rates of polymerization increased with an increase in EC and monomer concentrations: only at a higher concentration of EC (0.5 M) was a steep fall in R p observed for both monomer systems. The orders with respect to EC and monomer for MMA polymerization were 0.19 and 1.6, respectively. The orders with respect to EC and monomer for AN polymerization were 0.2 and 1.5, respectively. A kinetic scheme involving oxidation of EC by Ce(IV) via complex formation, whose decomposition gives rise to a primary radical, initiation, propagation, and termination of the polymeric radicals by biomolecular interaction is proposed. An oxidative termination of primary radicals by Ce(IV) is also included. 相似文献
7.
Prasant Kumar Jena Shilpa Singh Bhumika Prajapati G. Nareshkumar Tejal Mehta Sriram Seshadri 《Applied biochemistry and biotechnology》2014,172(8):3810-3826
The objective of present investigation was to study the effect of gut microbiota alteration by oral administration of targeted delivery of pH sensitive cefdinir microspheres to high-fructose-fed (HFD) rats. Rats were fed with a high-fructose diet with or without cefdinir microsphere administration for 30 days. The fecal microbiota community, oral glucose tolerance, the markers of liver injury, plasma and hepatic lipids profile, and histological evaluation were investigated. The levels of blood glucose, liver injury markers, lipid profile in plasma and liver, and fat tissue were significantly increased in high-fructose-fed rats. However, after pH-sensitive cefdinir microsphere administration, the elevation of these parameters was significantly suppressed. Cef EL significantly lowered the increased AST (p?<?0.05) and ALT (p?<?0.001) levels in HFD group. There is a significant lower (p?<?0.01) AUCglucose level in Cef EL group than HFD group The histological changes in the liver and the small and large intestines were more profound in HFD group as compared to cefdinir-treated HFD and control groups. Feeding of cefdinir microsphere sustained lactobacilli and bifidobacteria and significantly decreased (p?<?0.05) the number of Enterobacteriaceae induced by HFD. Experimental evidences demonstrated that the effectiveness of pH-specific cefdinir microsphere on reducing insulin resistance and development of metabolic changes in high-fructose-fed rats and suggested that it may be a promising therapeutic agent in treating type 2 diabetes. Intestinal-targeted antibiotic delivery needs to be further explored for its therapeutic applications. 相似文献
8.
A brief synthesis of endo-2-bromo-5-thiabicyclo [2.1.1]hexane ( 9 ) has been developed involving conversion of 3-cyclopentenol ( 6 ) to 3-thioacetoxycyclopentene ( 7 ), bromination of this giving trans-1,2-dibromo-4-thioacetoxycyclopentane ( 8 ), and treatment of the latter with base. Compound 9 is oxidized to its S-oxide 10 and S, S-dioxide 11 . Comparative 13C and 1H NMR data are given for 9–11 . 相似文献
9.
Lin C Chen C Sharkawy A Schneider GJ Venkataraman S Prather DW 《Optics letters》2005,30(11):1330-1332
We present a promising coupling device, namely, a terahertz (THz) planar photonic crystal (PhC) lens based on the effective refractive-index contrast between the PhC and the surrounding unpatterned area. Three-dimensional finite-difference time-domain calculations show a 90% power transfer from a 100-microm silicon waveguide to a 10-microm waveguide, and 45% coupling efficiency is confirmed experimentally. These results demonstrate the utility of the PhC lens as an effective approach to coupling into PhC THz circuits. 相似文献
10.
The structural stability and electronic properties of (ZnO)n, (NiO)n, (ZnO)n/(NiO)n for n = (1 to 4) and 3D structures were studied using density functional theory. The geometrical optimisation of clusters implies that when the atoms in the cluster increase it leads to an increase in its stability. The stability drastically increases for the heterostructure of (ZnO)n/(NiO)n. The dipole moment of the clusters depends on the geometry of the cluster and it is found to be minimum for heterostructures representing more neutralised clusters. HOMO-LUMO energies, ionisation potential, electron affinity, chemical hardness, binding energies and vibrational analysis of different clusters are calculated and reported. The adsorption of CO on the different sites of nanoclusters are studied and discussed. 相似文献