1,721,108 research outputs found
A review on ionic substitutions in hydroxyapatite thin films: Towards complete biomimetism
Full text linkPlasma sprayed coatings composed of stoichiometric hydroxyapatite have been extensively used to improve integration of metallic implants in the host bone, as hydroxyapatite (HA) is normally regarded as similar to the mineralized phase of bone. However, these coatings exhibited several drawbacks that limited their success. On the one hand biological apatite is a carbonated-HA, containing significant amounts of foreign ions, having low crystallinity and a small crystals size. This means that it differs from stoichiometric HA in terms of composition, stoichiometry, crystallinity degree, crystal size/morphology and, as a direct consequence, solubility, and ions release in the peri-implant environment. On the other hand, thick plasma sprayed coatings can undergo cracking and delamination and are scarcely uniform. For these reasons, research is pushing into two directions: (i) Increasing the similarity of apatite coatings to real bone, and (ii) exploring deposition by alternative plasma assisted techniques, allowing to achieve thin films, and having superior adhesion and a better control over the coating composition. In this article, we review the latest advances in the field of plasma-assisted deposition of ion-substituted hydroxyapatite thin films, highlighting the state of the art, the limitations, potentialities, open challenges, and the future scenarios for their application
Germination data of four Mediterranean species of coastal sand dunes
Full text linkThe present work gathers new germination assays of four Mediterranean species of coastal sand dunes. The studied species are: Anthemis maritima L. subsp. maritima, Crucianella maritima L., Eryngium maritimum L. and Thinopyrum junceum (L.) Á.Löve. Seeds were collected at the time of natural seed dispersal in two sites in the South of Sardinia. The germination tests were carried out at the Sardinian Germplasm Bank (BG-SAR). Our results show a high germination capability and germination rate for the tested plant species
Pollen micromorphological traits of the Tyrrhenian Stachys salisii Jord. & Fourr. (Lamiaceae)
No full textpollen micromorphology of plants from four populations of the tyrrhenian insular endemic Stachys salisii is examined using light and
scanning electron microscopy. the preliminary results show some differences between the populations analyzed as regards pollen surface
micromorphology and dimensions. the basic shape of the pollen grains is subprolate, usually tricolpate, but also oblate-spheroidal and tetracolpate.
the pollen surface is microreticulate, perforate or foveolate. Lumina are separated by smooth or sinuate muri, which make them polygonal and
elongate, while the number of punctae for each lumen also show some variations
La crisi dell'autorità nella scuola italiana. Alcune riflessioni sulla situazione attuale
No full textIndagine filosofica sul concetto di autorità e sulla sua crisi nella scuola italiana attuale, condotta alla luce di nozioni attinte da Platone, Kant e Hanna Arend
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