The orchid genus Dipteranthus, described by Rodrigues in 1882, comprises about 10 species distributed from Venezuela to Bolivia and Brazil. Plants of Dipteranthus are small epiphytes, reaching in total up to 10 cm in length, hence, are easily overlooked in the field. Modern classification of Dipteranthus is still under discussion. During the revision of orchids of the Guianas, we came across some specimens that do not match morphological characters of any previously known Dipteranthus species. Thus, we propose that these specimens represent a new species – Dipteranthus clarkei sp. nov. D. clarkei is the first representative of the genus known from Guyana.
The Pechini sol-gel method was applied to obtain LiMn2–xTxO4 (T = Ni, Fe; x = 0.1 to 0.5) nanopowders. Crystal and electronic structures, chemical composition and magnetic properties of the materials were characterized by X-ray diffraction, XPS, SEM/EDX microscopy, prompt gamma-ray activation analysis (PGAA), Mössbauer spectroscopy and magnetic susceptibility, respectively. XRD measurements showed that the LiMn2–xNixO4 were single phase for x = 0.1 and 0.2. Three samples with higher Ni content contained some addition of a second phase. Analysis of the oxidation state of the dopants by XPS revealed ionic Ni2+ and Fe3+. Mössbauer spectroscopy also confirmed 3+ oxidation state of iron and its location in octahedral sites, which excluded the inverse spinel configuration. XPS examinations showed that Mn3+ ions dominated in the iron substituted series whereas the Mn4+ was dominant in the nickel series.