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1.
Development of an Al-Mn-Be-Cu alloy with improved quasicrystalline forming ability
Franc Zupanič, Tonica Bončina, Niko Rozman, Ivan Anžel, Werner Grogger, Christian Gspan, Ferdinand Hofer, Boštjan Markoli, 2008, original scientific article

Abstract: An Al94Mn2Be2Cu2 cast alloy was developed displaying increased quasicrystalline formation ability at moderate cooling rates. The as-cast microstructure consisted of a mainly icosahedral phase in the Al-matrix. The microstructure remained stable during uniform heating to 580 °C and isothermalannealing at 400 °C. Most of the icosahedral phase was preserved even after 24 h annealing at 500 °C. For that reason, this alloy presents a promising basis for further development of cast Al-alloys containing quasicrystals.
Keywords: alluminium alloys, casting, quasicrystals, TEM, SEM
Published: 31.05.2012; Views: 1138; Downloads: 64
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2.
Structure of the Malpighian tubule cells and annual changes in the structure and chemical composition of their spherites in the cave cricket Troglophilus neglectus Krauss, 1878 (Rhaphidophoridae, Saltatoria)
Saška Lipovšek Delakorda, Ilse Letofsky-Papst, Tone Novak, Ferdinand Hofer, Maria Anna Pabst, 2009, original scientific article

Abstract: Periodical changes in the structure of spherites in the Malpighian tubule cells of the cave cricket Troglophilus neglectus were studied to elucidate their role during the cricket's life cycle in natural circumstances. Special interest was given to the dormant overwintering period when we hypothesized that the primary role of spherites is to supply minerals for basic vital processes. The investigation was carried out by light and transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy-loss spectroscopy and energy-filtering TEM. Spherites are present only in the middle Malpighian tubule segment, consisting of Type 1 cells, characterized, among other features, by a round, apically placed nucleus and numerous spherites, and a few Type 2 cells with an elongated nucleus in the centre and sparse spherites. At the beginning of dormancy in November juveniles, minerals are accumulated in spherites and then decline until March.In one-year-old May larvae, spherites are commonly rich in minerals, and from July onwards they are progressively exploited in the adults. Spherite destruction starts with apoptosis in senile October individuals. The findings suggest that the mineral supply of spherites in Malpighian tubules is crucial to supporting vital processes throughout the life cycle of T. neglectus.
Keywords: biology, zoology, cells, spherites, insects, Troglophilus neglectus, analysis
Published: 07.06.2012; Views: 1178; Downloads: 55
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3.
Application of elemental microanalysis to elucidate the role of spherites in the digestive gland of the helicid snail Chilostoma lefeburiana
Saška Lipovšek Delakorda, Ilse Letofsky-Papst, Tone Novak, Manuela Giovannelli, Ferdinand Hofer, Maria Anna Pabst, 2008, original scientific article

Abstract: In this case study we present an application of different analytical electron microscopic methods in biology, to elucidate their usefulness in such investigations. Using analytical electron microscopy, spherites in the digestive gland cells of the helicid snail Chilostoma lefeburiana were examined at three stages: just before the non-feeding period of over-wintering in November, in the middle of over-wintering in February and at its end in March. A detailed characterization of changes in the elemental composition of the spherites was characterized by a combination of transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDXS), electron energy-loss spectroscopy (EELS) and energy filtering TEM (EFTEM). During over-wintering, the spherites passed the following changes. Before over-wintering in November, they consisted of striking concentric layers of electron-dense and electron-lucent zones, while in February and March they showed clear empty zones between materials of different electron density. In November spherites, C, O, Ca, P, Cl, Fe, Si, Na, K, Mg and S were detected, whereas in February ones C, O, N, Cl, Si and S were found and only C, O, N, Si and Cl were detected in March spherites. It is suggested that the elements missing in February and March were used in different physiological processes during over-wintering, like (1) the maintenance of the appropriate elemental composition of the internal environment, (2) accumulation of non-toxic waste materials that cannot be metabolized and (3) avoiding potential intoxication by contamination with toxic metals.
Keywords: zoology, Chilostoma lefeburiana, snails, digestive gland, over-wintering, spherites, elemental analyses, environmental pollution, chemical structures
Published: 07.06.2012; Views: 925; Downloads: 50
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