937 resultados para Caos espaço-temporal
Resumo:
Several countries have made large investments in building historical Geographical Information Systems (GIS) databases containing census and other quantitative statistics over long periods of time. Making good use of these databases requires approaches that explore spatial and temporal change.
Resumo:
Background The spontaneously hypertensive rat (SHR) is frequently used as model of cardiovascular disease, with considerable disparity in reported parameters of hypertrophy. The aim of this study was to assess the temporal changes occurring during the development and progression of cardiomyocyte hypertrophy in SHR, subsequent to pressure overload, compared to changes associated with normal aging using the normotensive Wistar–Kyoto (WKY) rat. Methods Ventricular cardiomyocytes were isolated from rats at 8, 12, 16, 20 and 24 weeks, and parameters of hypertrophy (cell dimensions, protein mass, de novo protein synthesis, and gene expression) and function (contraction and hypertrophic responsiveness in vitro) were assessed. Results Hypertension was evident at =7 weeks in SHRs. Heart:body mass ratio, cardiomyocyte protein mass and width were elevated (P
Resumo:
Reproducible modulations in low-pressure, inductively coupled discharges operating in chlorine and argon-chlorine mixtures have been observed and studied. Changes in the light output, floating potential, negative ion fraction, and charged particle densities were observed. Here we report two types of unstable operational modes in an inductively coupled discharge. On the one hand, when the discharge was matched, to minimize reflected power, instabilities were observed in argon-chlorine plasmas over limited operating conditions of input power and gas pressure. The instability window decreased with increasing chlorine content and was observed for chlorine concentrations between 30% and 60% only. However, when operating at pressures below 5 mTorr and the discharge circuit detuned to increase the reflected power, modulations were observed in a pure chlorine discharge. These modulations varied in nature from a series of sharp bursts to a very periodic behavior and can be controlled, by variation of the matching conditions, to produce an apparent pulsed plasma environment. (C) 2005 American Institute of Physics.
Resumo:
The European otter (Lutra lutra L.) has a highly specialised diet that is composed predominantly of fish. The current study investigates the percentage composition of food items in otter spraints collected in six river catchments in Northern Ireland in 1980 and again from the same locations in 2003. Spraints contained significantly more salmonids than any other prey item. The composition of spraints differed among catchments. More salmonids and three-spined stickleback (Gasterosteus aculeatus L.) were found in spraints from the Glens of Antrim, while spraints from the Lagan catchment had significantly more eel (Anguilla anguilla L.). There were significantly more spraints containing non-fish food items in 2003 compared with 1980. These non-fish items were insects, amphipods, birds, rats (Rattus norvegicus Berkenhout) and lagomorphs. Increased consumption of non-fish items was apparent in all but one of the river catchments. The mean diversity of spraint composition was significantly greater in 2003 than in 1980. Therefore, our findings indicate that otters have diversified their diet since 1980 and now eat more non-fish prey.