Browsing by Author "Bobos, Iuliu"
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- Biomineralization studies on cellulose membrane exposed to biological fluids of Anodonta cygneaPublication . Lopes, Anabela; Lima, Manuel Lopes; Ferreira, Jorge Amaral; Araújo, Sandra; Hinzmann, Mariana F.; Oliveira, José; Rocha, António; Domingues, Bernardo; Bobos, Iuliu; Machado, JorgeThe present work proposes to analyse the results obtained under in vitro conditions where cellulose artificial membranes were incubated with biological fluids from the freshwater bivalve Anodonta cygnea. The membranes were mounted between two half ‘Ussing chambers’ with different composition solutions in order to simulate epithelial surfaces separating organic fluid compartments. The membrane surfaces were submitted to two synthetic calcium and phosphate solutions on opposite sides, at pH 6.0, 7.0 or 9.0 during a period of 6 hours. Additional assays were accomplished mixing these solutions with haemolymph or extrapallial fluid from A. cygnea, only on the calcium side. A selective ion movement, mainly dependent on the membrane pore size and/or cationic affinity, occurred with higher permeability for calcium ions to the opposite phosphate chamber supported by calcium diffusion forces across the cellulose membrane. In general, this promoted a more intense mineral precipitation on the phosphate membrane surface. A strong deposition of calcium phosphate mineral was observed at pH 9.0 as a primary layer with a homogeneous microstructure, being totally absent at pH 6.0. The membrane showed an additional crystal phase at pH 7.0 exhibiting a very particular hexagonal or cuttlebone shape, mainly on the phosphate surface. When organic fluids of A. cygnea were included, these crystal forms presented a high tendency to aggregate under rosaceous shapes, also predominantly in the phosphate side. The cellulose membrane was permeable to small organic molecules that diffused from the calcium towards the phosphate side. In the calcium side, very few similar crystals were observed. The presence of organic matrix from A. cygnea fluids induced a preliminary apatite–brushite crystal polymorphism. So, the present results suggest that cellulose membranes can be used as surrogates of biological epithelia with preferential ionic diffusion from the calcium to the phosphate side where the main mineral precipitation events occurred. Additionally, the organic fluids from freshwater bivalves should be also thoroughly researched in the applied biomedical field, as mineral nucleators and crystal modulators on biosynthetic systems.
- Geoquímica ambiental em áreas mineiras abandonadas do Norte de Portugal [Resumo]Publication . Bobos, Iuliu; Ávila, Paula Freire; Costa, Maria do Rosário; Silva, E. Ferreira da; Durães, Nuno
- Morphological and chemical characterization of mineral concretions in the freshwater bivalve Anodonta cygnea (Unionidae)Publication . Hinzmann, Mariana F.; Lima, Manuel Lopes; Bobos, Iuliu; Ferreira, Jorge Amaral; Domingues, Bernardo; Machado, JorgeThe freshwater mussel Anodonta cygnea is commonly used as a model organism for biomineralization studies, its peculiar morphofunctional properties also make it an excellent environmental biomonitor. The first detailed on the calcareous concretions from gill and mantle tissue, as well as fluids of the freshwater bivalve A. cygnea, supported by histological, scanning, spectrometry, and spectroscopy analyses. Through these analyses, the morphology, structure, and chemical characterization of these biomineral concretions were accomplished. The concretions represent a high percentage of the dry weight of these organisms. In gill tissue, it can reach up to 50% of dry weight prior to reproductive maturity. Analysis of elemental composition of the tissue concretions showed the presence of calcium and phosphate, as main components, associated with other residual elements like iron, manganese, magnesium, and zinc. Concretions are arranged in concentric alternated layers of organic and inorganic matrix. The shape and size of the concretions vary substantially, from very small, less than 1 µm diameter with very regular round structure, found mainly in the mantle tissue, to more than 50 µm length with irregular globular clusters, found predominantly in the gills. The microstructural organization is of a hydroxyapatite polymorphism in the mantle, in contrast to the gills, which exhibit irregular structure and carbonated hydroxyapatite polymorphism. These differences are supported by higher contents of dinitrogen pentoxide, magnesium, and iron in the mantle concretions, but higher contents of manganese and zinc in the gills. Furthermore, the results indicate that the mineral concretion formation in A. cygnea is a hemocytes reaction to particle or toxic invasions. A second relevant role, concerns the close involvement of these microspherules on the adult and larval shell calcification.
- Rare Earth Elements fractionation in native vegetation from the Moncorvo iron mines, NE PortugalPublication . Durães, Nuno; Silva, Eduardo Ferreira da; Bobos, Iuliu; Ávila, Paula FreireFractionation of Rare Earth Elements (REE) and the accumulation and translocation indexes were measured and determined in the native vegetation [Halimium lasianthum (Lam.) Spach subsp. alyssoides (Lam.) Greuter; Cytisus multiflorus (L’Hér.) Sweet; and Cistus monspeliensis L.; Cistus ladanifer subsp. ladanifer; Lavandula stoechas L.] from the iron mining area of Moncorvo (NE Portugal). There is no correlation between the amounts of REE in rhizosphere and in plants. The REE concentration as the fractionation follows roots>leaves>stems in plants. A slightly enrichment in HREE were found in rhizosphere and plants (roots and stems), whereas the leaves are enriched in LREE. The accumulation and translocation depend of internal complexes ligands. The redox and pH conditions of the rhizosphere conditioned the REE uptake. Greatest bioaccumulation ability of heavy REE (HREE) was found in C. monspeliensis, followed by H. lasianthum that also, has a high capacity of the REE translocation to the aerial parts, contrary to C. monspeliensis. An M-type tetrad effect was determined mainly for HREE (Gd-Ho series) indicating a complexation of REE. The greatest differences in the REE fractionation patterns (mainly for HREE) are observed in stems, as a consequence of the transport function of this organ. Cerium anomaly indicates that the pH and redox conditions affected the uptake of Ce by plants, where the free ionic species are dominated in roots and leaves (positive anomaly), and stems (negative anomaly). Also the Eu-anomaly is greater in roots and leaves than in steams probably by participation in metabolic functions due to similarity with calcium.
- Serpentine-to-chlorite transformation in serpentinized ultrabasic rocks from the Upper Allochthonous Terrane of the Bragança Complex, NE PortugalPublication . Ínsua-Pereira, G.; Bobos, Iuliu; Meireles, CarlosABSTRACT: A transformação de serpentina para clorite foi identificada nas rochas ultrabásicas serpentinizadas do Maciço de Bragança, NE de Portugal. O principal objetivo deste trabalho consiste na caracterização estrutural, cristaloquímica e termodinâmica desta reação. Os espetros de DRX obtidos permitem a identificação de lizardite (d[hkl] = 7.32 Å, 4.55 Å, 3.65 Å, 2.65 Å, 2.45 Å, 2.09 Å, 1.74 Å, 1.53 Å) e clorite (d[hkl] = 14.25 Å, 7.14 Å, 4.71 Å, 3.55 Å, 2.83 Å). As composições cristaloquímicas gerais obtidas a partir de EPMA são de (Mg2.65-2.79, Fe0.08-0.20, Al0.01-0.06)(Si1.94-2.07, Al0-0.06)O5(OH)4 para a serpentina e de (Mg2.84, Fe1.79, Al1.23)(Si2.82, Al1.18)O10(OH)8 para uma Mg,Fe clorite. A reação mineralógica terá resultado da ação de fluidos hidrotermais a temperaturas de aproximadamente 350 (±50) ºC, num evento pós-serpentinização, responsável pela transformação da serpentina em Mg,Fe-clorite através de um processo de dissolução e cristalização.
- Visita ao Campo Mineiro de JalesPublication . Bobos, Iuliu; Ávila, Paula Freire; Silva, Eduarda Moreira da; Durães, Nuno