1,107 research outputs found
ANATOMIA, HISTOQUÍMICA E PROSPECÇÃO FITOQUÍMICA DE FOLHAS E RAIZ DE Senna occidentalis (L.) Link e Senna reticulata (Willd.) H. S. IRWIN & BARNEBY USADAS NO TRATAMENTO DE MALÁRIA NA AMAZÔNIA
Malária é uma doença que preocupa as entidades de saúde nos países tropicais pelo número crescente de casos e pela resistência parasitária do protozoário infectante e do mosquito transmissor a inseticidas. Senna occidentalis e S. reticulada são utilizadas no tratamento e profilaxia da malária e o objetivo desse trabalho foi identificar substâncias quimicamente ativas em células e/ou tecidos dessas espécies. Análises anatômicas, histoquímicas e fitoquímicas foram feitas segundo metodologias usuais. As folhas de S. occidentalis e S. reticulata são semelhantes em relação à estrutura anatômica, diferenciando-se na presença de tricomas glandulares em S. occidentalis, papilas na epiderme de S. reticulata, e na composição histoquímica. As raízes das duas espécies analisadas também se assemelham, destacando-se a presença de fibras gelatinosas, cristais prismásticos e drusas. A prospecção fitoquímica revelou cumarinas, flavanonas, catequinas, esteroides livres, saponinas e bases quaternárias
Evidence for Blue Straggler Stars Rejuvenating the Integrated Spectra of Globular Clusters
Integrated spectroscopy is the method of choice for deriving the ages of
unresolved stellar systems. However, hot stellar evolutionary stages, such as
hot horizontal branch stars and blue straggler stars (BSSs), can affect the
integrated ages measured using Balmer lines. Such hot, "non-canonical" stars
may lead to overestimations of the temperature of the main sequence turn-off,
and therefore underestimations of the integrated age of a stellar population.
Using an optimized Hbeta index in conjunction with HST/WFPC2 color-magnitude
diagrams (CMDs), we show that Galactic globular clusters exhibit a large
scatter in their apparent "spectroscopic" ages, which does not correspond to
that in their CMD-derived ages. We find for the first time that the specific
frequency of BSSs, defined within the same aperture as the integrated spectra,
shows a clear correspondence with Hbeta in the sense that, at fixed
metallicity, higher BSS ratios lead to younger "apparent" spectroscopic ages.
Thus, the specific frequency of BSSs in globular clusters sets a fundamental
limit on the accuracy for which spectroscopic ages can be determined for
globular clusters, and maybe for other stellar systems like galaxies. The
observational implications of this result are discussed.Comment: 5 pages, 2 figures, 1 table. Accepted for publication in ApJ
Journals’ policies of storage and reuse of raw research data and their impact in five scientific areas
Analisys of journals' policies about storage and re-use of raw research data
Journals’ policies of storage and reuse of raw research data and their impact in five scientific areas
Analisys of journals' policies about storage and re-use of raw research data
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