Trailing Vortex Wake Encounters at Altitude - A Potential Flight Safety Issue?

The potential hazard of one aircraft encountering the trailing vortex wake of another aircraft during either take-off or landing is well known. The wake vortex hazard in the terminal area has been virtually eliminated using the operational procedures and aircraft separation criteria mandated by the air traffic authorities. This paper presents arguments that wake encounters at cruise altitude are a potential safety issue that needs to be examined. Wake vortex encounters at cruise altitudes are likely to increase due to three factors. These factors include; the reduction of the minimum vertical separation distances between aircraft, the increased air traffic allowed by the reduced vertical separations, and the large difference in the size of aircraft operating at the cruise altitudes. The arguments are supported by simple analysis and a review of simulation and flight test results obtained from earlier studies of wake encounters at low altitudes. Simple analysis techniques show that the rolling moment induced on a following aircraft is comparable in magnitude to that which could occur during take-off or landing. In addition reported wake encounters at cruise altitude are discussed

Orchidaceae das Serras Negra e do Funil, Rio Preto, Minas Gerais, e similaridade florística entre formações campestres e florestais do Brasil

Neste estudo, foi realizado o levantamento das Orchidaceae das Serras Negra e do Funil (SN/SF), Zona da Mata de Minas Gerais, e uma análise da similaridade florística dessa família entre 29 áreas campestres e florestais do Brasil. Para tal análise, utilizou-se o algoritmo UPGMA, coeficiente de SØrensen, e 5.000 replicações de bootstrap. A análise de agrupamento revelou baixos índices de similaridade, exceto para os grupos Serra Negra + Parque Estadual do Ibitipoca e Parque Estadual da Ilha do Cardoso + Estação Ecológica Juréia-Itatins. Os resultados sugerem que a região das SN/SF represente um corredor florístico entre localidades na Serra da Mantiqueira (Parque Nacional do Itatiaia) e Serra do Mar (Reserva Biológica de Macaé de Cima). Foi observado o agrupamento de áreas com semelhanças ambientais e as regiões de campos rupestres se destacaram em termos de particularidades florísticas. O teste de Mantel revelou que a similaridade florística não está correlacionada à distância geográfica entre as áreas.This study presents a survey of the Orchidaceae from Serra Negra and Serra do Funil (SN/SF), 'Zona da Mata', Minas Gerais state, and analyzes the floristic similarity of this family among 29 grassland and forest sites in Brazil. Cluster analysis used the UPGMA algorithm, SØrensen coefficient, and bootstrap analyses with 5,000 replications. The cluster analyses revealed low similarity indices; exceptions are the clusters composed of Serra Negra + Ibitipoca State Park and Ilha do Cardoso State Park + Juréia-Itatins Ecological Station. The results suggest that SN/SF represents a floristic corridor between sites in Serra da Mantiqueira (Itatiaia National Park) and Serra do Mar (Macaé de Cima Biological Reserve). Groups of areas with similar environmental conditions were observed and the "campos rupestres" regions stood out because of their singular floristic composition. The Mantel test revealed that floristic similarity is not associated with geographic distance between the areas