18,279 research outputs found
Self-similar fractals and common hypercyclicity
We obtain a multi-dimensional generalization of the Costakis-Sambarino
criterion for common hypercyclic vectors with optimal consequences on a large
class of fractals. Applications include families of products of backward shifts
parameterized by any H\"older continuous curve in , for all .Comment: 31 pages, 14 figure
Stellar populations in superclusters of galaxies
A catalogue of superclusters of galaxies is used to investigate the influence
of the supercluster environment on galaxy populations, considering galaxies
brighter than M-21+5 h. Empirical spectral synthesis techniques are
applied to obtain the stellar population properties of galaxies which belong to
superclusters and representative values of stellar population parameters are
attributed to each supercluster. We show that richer superclusters present
denser environments and older stellar populations. The galaxy populations of
superclusters classified as filaments and pancakes are statistically similar,
indicating that the morphology of superclusters does not have a significative
influence on the stellar populations. Clusters of galaxies within superclusters
are also examined in order to evaluate the influence of the supercluster
environment on their galaxy properties. Our results suggest that the
environment affects galaxy properties but its influence should operate on
scales of groups and clusters, more than on the scale of superclusters.Comment: 7 pages, 4 figures; accepted to MNRA
Analysis of Modal Behavior at Frequency Cross-Over
The existence of the mode crossing condition is detected and analyzed in the Active Control of Space Structures Model 4 (ACOSS4). The condition is studied for its contribution to the inability of previous algorithms to successfully optimize the structure and converge to a feasible solution. A new algorithm is developed to detect and correct for mode crossings. The existence of the mode crossing condition is verified in ACOSS4 and found not to have appreciably affected the solution. The structure is then successfully optimized using new analytic methods based on modal expansion. An unrelated error in the optimization algorithm previously used is verified and corrected, thereby equipping the optimization algorithm with a second analytic method for eigenvector differentiation based on Nelson\u27s Method. The second structure is the Control of Flexible Structures (COFS). The COFS structure is successfully reproduced and an initial eigenanalysis completed
Anthropogenic nutrient pollution of coral reefs in Southern Bahia, Brazil
Este artigo discute os fatores espaço, tempo e atividade antrópica na distribuição de nutrientes em amostras dos recifes costeiros da Baía de Porto Seguro, sul do Estado da Bahia. Análises realizadas nas amostras d'água incluem a porção reativa de nitrogênio (TON), fósforo (SRP) e silicato (DSi) dissolvidos, e clorofila (Chl). Resultados indicam um aumento significante (F=19.873, pSpatial, temporal and anthropogenic controls on nutrient distribution were evaluated for nearshore and offshore reefs at Porto Seguro Bay, Southern Bahia. Water samples were analysed for total oxidised nitrogen (TON), soluble reactive phosphorus (SRP), reactive silica (DSi), and chlorophyll a (Chl). The results indicate that rainfall promotes a significant (F=19.873,
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