1,721,034 research outputs found
Isotopic effect on the kinetics of the Belousov-Zhabotinsky reaction: Cerium-Malonic subsystem.
No full textEffect of medium viscosity in a closed unstirred Belousov-Zhabotinsky system
No full textComplex periodic and aperiodic behaviors are reported in an unstirred Belousov–Zhabotinsky oscillatory reaction
containing different concentrations of polyethylene-glycol. A route from chaos following an inverse Ruelle–Takens–New-
house RTN. scenario is identified. Thus, hydrodynamic effects, being mainly convective, seem to be responsible for the
observed RTN scenario. We demonstrate that the medium viscosity, namely the polyethylene-glycol concentration, is a
bifurcation parameter for the sequence chaos --> quasi-periodicity --> period-1. reserved
Exploring Gas Evolution Oscillators: Mechanisms and Applications
No full textWe review an iconic class of chemical oscillators driven by phase transition instabilities, namely Gas Evolution Oscillators (GEOs). These systems show oscillatory dynamics in the delivery of gas sustained simple reactions yielding gaseous products in a liquid mixture, due to nucleation and supersaturation phenomena. After presenting the main features and properties of these systems, we deepen the underlying mechanism through a unified picture of the various models that have been proposed to describe this kind of oscillations. We finally discuss a concrete example of how such instabilities can impact chemical processes with applied relevance
Exergy versus emergy flow in ecosystems: is there an order in maximizations?
No full textFrom ecosystems theory, orientors have been derived to give a holistic view of the trend of development of ecosystems themselves. Several principles of maximization, mainly derived from Lotka's maximum power, are connected with these orientors. Other authors (Jørgensen, Patten and coworkers, for example) have shown that among these orientors there are many common aspects, both form a quantitative terms and in principle. We show how H.T. Odum's maximum empower and Jørgensen's maximum exergy principles can be both valid from a practical viewpoint. As suggested by a simple experiment there can be a time order: first the maximization of empower and then the maximization of exergy. This time sequence is also consistent with a maximization trend in the ratio of exergy to empower. © 2005 Elsevier Ltd. All rights reserved
A ternary bifurcation diagram for a closed unstirred cerium catalyzed Belousov-Zhabotinsky System in function of the percent in volume of the major components of the system
No full textNMR structural investigation of the biotin-avidin complex: A C-13 NMR paramagnetic relaxation study
No full textThe paramagnetic contributions to the spin-lattice relaxation rates of biotin C-13 nuclei, induced by the presence in the water/DMSO solution of the TEMPOL nitroxide, have been analysed in the interaction with avidin. The paramagnetic relaxation data, obtained at different temperatures, indicate that the average solvent/spin-label exposure of biotin carbons is consistent with the conformational features previously observed for the complex in the crystal. The analysis of the paramagnetic perturbation profiles, derived from C-13 spin lattice relaxation measurements, seems to be highly informative of the sterical aspects of interaction processes of large biopolymers with their ligands
Sequence homology between HIV gp120, rabies virus glycoprotein, and snake venom neurotoxins. Is the nicotinic acetylcholine receptor an HIV receptor?
No full textWe have found a striking homology between the sequence 164-174 of HIV-1 gp120 and the sequence 30-40 of snake venom neurotoxins; this sequence homology is very similar to that existing between the same region of snake venom neurotoxins and rabies virus glycoprotein. © 1990 Springer-Verlag
Single step purification of a synthetic peptide fragment of neurofilaments by preparative high performance liquid-chromatography
No full textIt was recently shown that fragment Lys-Ser-Pro-Val (1,2) is the major site in vivo neurofilament phosforilation. A suitable method for the preparation of this peptide was therefore studied paying particular attention to the purification step. Even thought solubility of this peptide in methyl t-butil ether does not allow the standard purification. It is possible achieve a good separation in a single step by HPLC, after a simple extraction with acidic water.It was recently shown that fragment Lys-Ser-Pro-Val (1,2) is the major site in vivo neurofilament phosforilation. A suitable method for the preparation of this peptide was therefore studied paying particular attention to the purification step. Even thought solubility of this peptide in methyl t-butil ether does not allow the standard purification. It is possible achieve a good separation in a single step by HPLC, after a simple extraction with acidic water. © 1989, Taylor & Francis Group, LLC. All rights reserved
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