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New insights into the anatomy of an endemic Hladnikia pastinacifolia Rchb.
Nina Šajna, Jelka Šuštar Vozlič, Mitja Kaligarič, 2014, izvirni znanstveni članek

Opis: We studied the anatomy of a rare narrow endemic species belonging to the Slovenian flora - Hladnikia pastinacifolia Rchb. Hladnikia is a monotypic genus with distinct taxonomic position within the Apiaceae family. The anatomical characteristics revealed by light and fluorescence microscopy provided new insights regarding the pollen, leaf and root characteristics of H. pastinacifolia, improving the understanding of its biology and ecology. Pollination, drought tolerance, life cycle and unattractiveness to herbivores explain the species' persistence in time. Autofluorescence localized bioactive substances within secretory ducts and oil ducts.
Ključne besede: Hladnikia pastinacifolia, endemic plants, petiole anatomy, pollen
Objavljeno: 28.03.2017; Ogledov: 20; Prenosov: 0
.pdf Polno besedilo (348,70 KB)

Micropropagation of the narrow endemic Hladnikia pastinacifolia (Apiaceae)
Jana Ambrožič-Dolinšek, Terezija Ciringer, Mitja Kaligarič, 2016, izvirni znanstveni članek

Opis: The monotypic Hladnikia pastinacifolia Rchb. is a narrow endemic species, with an extremely small distribution area in Slovenia, prone to any kind of threat that could lead to species extinction. Tissue culture techniques are proposed as a conservation measure for rapid propagation and ex-situ conservation. Tissue culture was initiated from seeds and juvenile plants obtained from natural sites on a solid Murashige and Skoog (MS) medium, with and without growth regulators. We tested various combinations and concentrations of growth regulators, and the best proliferation of axillary shoots, on average 14, was obtained on MS medium with 5 μM BAP and 3 μM IBA and 3% sucrose. Rooting was achieved after transferral of the shoots to an MS medium with 2 μM IBA and 3% sucrose. The rooted plants were acclimatized on a mixture of limestone sand, potting soil and vermiculite in a ratio of 10:2:2, with pH in the range of 7.5–8.0. In vitro propagation methods provide an important opportunity for the propagation and preservation of H. pastinacifolia by rapidly increasing the number of plants, without disturbing the wild population.
Ključne besede: biotechnology, micropropagation, micropropagation, tissue culture, Hladnikia pastinacifolia, Apiaceae
Objavljeno: 28.03.2017; Ogledov: 19; Prenosov: 0
.pdf Polno besedilo (392,24 KB)

Least adder's-tongue (Ophioglossum lusitanicum L.) in Croatia - distribution, ecology and conservation
Slavko Brana, Nina Vuković, Mitja Kaligarič, 2014, izvirni znanstveni članek

Opis: The presence of the least adder's tongue (Ophioglossum lusitanicum) in Croatia is sparsely documented in scientific literature, with only a few records to date. After findings from the 19th century, the species was not confirmed in the field for a whole century, and was consequently considered extinct in the Croatian flora. It has been recently confirmed in southern Istria (Croatia), in habitats with moderate anthropogenic impacts.
Ključne besede: Croatia, distribution, endangered species, flora, Istria, Ophioglossum lusitanicum
Objavljeno: 28.03.2017; Ogledov: 16; Prenosov: 0
.pdf Polno besedilo (304,26 KB)

Germination characteristics of Salicornia patula Duval-Jouve, S. emerici Duval-Jouve, and S. veneta Pign. et Lausi and their occurrence in Croatia
Nina Šajna, Marjana Regvar, Simona Kaligarič, Željko Škvorc, Mitja Kaligarič, 2013, izvirni znanstveni članek

Opis: According to recent molecular analyses of Salicornia, we revised the annual glassworts from the Croatian coast, classified until now only as Salicornia europaea. Two species, a diploid Salicornia patula and a tetraploid S. emerici were recognized. They can be easily distinguished by floral characters, but not only by their habitus, which varies extremely according to environmental factors. Both species differ also in seed morphology. Salicornia patula has dimorphic seeds, with larger central seeds reaching high germination rates. Germination patterns helped to explain the habitat preferences. The species rarely co-occur, however. The rare S. patula occupies drier habitats, on coastal mudflats or sands that are irregularly inundated. It occurs within the assoc. Suaedo maritimae-Salicornietum patulae. Salicornia emerici occupies the lowest coastal mudflats, regularly inundated, where nutrient-rich conditions prevail, and forms an almost monotypical assoc. Salicornietum emerici. Due to the synonymy of S. veneta with S. emerici, we exclude the occurrence of S. veneta in Croatia as an independent taxon.
Ključne besede: botany, vegetation, Croatia
Objavljeno: 28.03.2017; Ogledov: 19; Prenosov: 1
.pdf Polno besedilo (296,66 KB)

The influence of the morphology of iron powder particles on their compaction in an automatic die
Borivoj Šuštaršič, Matjaž Godec, Črtomir Donik, Irena Paulin, Srečko Glodež, Marko Šori, Milan Ratej, Nada Javornik, 2015, strokovni članek

Opis: Fe- and steel-based powder metallurgy (P/M) products, such as steel gears, spurs, locking mechanisms, porous filters, sliding bearings and bushes, as well as other machine parts and structural elements, are mainly produced with the so-called conventional sintering technology. It is the most efficient technology for the mass production of small, complex, functional and structural parts. Therefore, it is the most convenient and popular among all of the P/M technologies. The most important end-user of sintered parts is the automotive industry. However, small, complex, sintered parts can also be frequently used in the furniture and household industries, precise mechanics, articles for recreation and sports. A fine, iron-based powder mixture or prealloyed powder is first automatically uniaxial-die compacted (ADC) into the final shape of the product with a mechanical or hydraulic press and then sintered in a protective atmosphere at approximately 1100 °C. The metal powder mixture must have the appropriate engineering properties given by the chemistry and particle morphology, enabling a fast and reliable die-compaction process. The most important are a high tap density, a good powder flowability and a low compressibility. All this gives the green compacts an appropriate final shape with a smooth surface, a relatively high and uniform green density, as well as a green strength without internal flaws and cracks. In the case of very small two-or-more-heights products, for example, spur gears with a low module, it is very difficult to obtain a uniform green density at acceptable compaction pressures. Often small cracks are formed at height crossings and big differences in the green density appear in smaller or thinner regions. In the frame of our investigation we analysed the influence of the selected prealloyed commercial iron powder’s morphology and its technological properties on automatic die compaction, as well as the sintering process in the case of small two-level sintered gear dimensions of 5/40–7/10×7mm with module m = 0.5. The original iron powder was sieved and the finest powder particle fraction (< 45 µm) was compared with the original powder mixture considering ADC and sintering process. It was found that the selection of the finer powder mixture could not contribute to the improvement in the overall ADC process, as well as a better green compact. In the present paper the results of our investigations are presented and the reasons why a finer powder mixture cannot contribute much to an improvement of the conventional sintering process.
Ključne besede: Fe-based alloy powders, particles, morphology, microstructure, automatic die compaction, sintering
Objavljeno: 27.03.2017; Ogledov: 12; Prenosov: 0
.pdf Polno besedilo (1,18 MB)

Morphological and microstructural features of Al-based alloyed powders for powder-metallurgy applications
Borivoj Šuštaršič, Irena Paulin, Matjaž Godec, Srečko Glodež, Marko Šori, Jože Flašker, Albert Korošec, Stanislav Kores, Goran Abramović, 2014, strokovni članek

Opis: Besides advanced nano steels, polymers and ceramics, recently also light metals, i.e., Al, Mg and Ti based materials, have been recognized as future materials for different kinds of advanced applications. Al and its alloys have an acceptable price, excellent corrosive resistance, good mechanical and other physical properties. Therefore, they are also used in the powder-metallurgy (P/M) field. The P/M technology of Al materials is very demanding and has its own specifics compared to the sintering technology of iron and steel. A relatively large quantity of Al-based alloy powder is formed during the sand blasting of slugs and discs in the Talum Al factory, Kidričevo, Slovenia. Therefore, we analysed and investigated its practical usability for a production of advanced products using P/M technology. The formed Al-based powder was compared with the commercially available Al-based powders that are generally used for conventional sintering technology. In the first part of this paper we explain which types of Al-based powders are used for the production of sintered parts, what the required parameters are and why we considered them. Then, the results of theoretical thermodynamic analyses and investigations of the morphological and microstructural characteristics of the selected commercial Al-based powders are given, as well as their comparison with the Al powder formed during the sand blasting and its potential for P/M applications.
Ključne besede: Al-based alloy powders, morphology, microstructure, LM characterisation, SEM/EDS characterisation
Objavljeno: 17.03.2017; Ogledov: 35; Prenosov: 0
.pdf Polno besedilo (4,85 MB)

Influence of transient response of platinum electrode on neural signals during stimulation of isolated swinish left vagus nerve
Polona Pečlin, Franci Vode, Andraž Mehle, Igor Grešovnik, Janez Rozman, 2012, izvirni znanstveni članek

Opis: The main aim of the work was to measure transient response characteristics of interface between platinum stimulating electrodes and isolated swinish left cervical vagus nerve (segment), when electrical stimulating pulses are appliedto preselected locations along the segment and elicited neural signals,also described as compound action potentials (CAPs), are recorded fromparticular compartments of the nerve. The stimulating system was manufactured as a silicone self-coiling spiral cuff (cuff) with embedded matrix of ninety-nine rectangular electrodes (0.5 mm in width and 2mm in length), made of 45 microm thick annealed platinum ribbon (99.99 % purity), and a geometric surface of 1 mm2. For electrical stimulation, a current quasitrapezoidal, asymmetric and biphasic pulses with frequency of 1 Hz, were used. To test an influence of stimulating pulses having different parameters and waveforms on elicited CAPs, various degree of imbalance between an electric charge (charge) injected in cathodic phase as well as charge injectedin anodic phase of a biphasic stimulating pulse, were deployed and compared. To identify the differences in elicited CAPs however, an integral ofthe CAP cathodic phase as well as integral of the CAP anodic phase of stimulating pulse, were calculated and compared. Results showed a strong component superimposed in the CAPs, considered as an ensemble artefact which greatly obscured the components of the CAPs, and various components did overlap. Results also showed that stimulating pulses, having preset certain degree of imbalance between charge injected in cathodic and charge injected inanodic phase, elicited a slight change in a positive waveform deflection of CAP manifested under a cathodic phase as well as slight change in a negative waveform deflection of CAP manifested under an anodic phase. (Abstract truncated at 2000 characters)
Ključne besede: electrical stimulation, platinum electrodes, left vagus nerve, electrochemistry, electrical charge
Objavljeno: 16.03.2017; Ogledov: 20; Prenosov: 0
.pdf Polno besedilo (179,34 KB)

Fatigue properties of sintered DIN SINT-D30 powder metal before and after heat treatment
Marko Šori, Borivoj Šuštaršič, Srečko Glodež, 2014, izvirni znanstveni članek

Opis: The main focus of this study was to determine how heat treatment affects the dynamic properties of sintered steel. All the specimens were made of the DIN SINT-D30 metal powder, but only half of them were additionally heat treated. Flat specimens were cold pressed and sintered. The second set was additionally heat treated to increase the strength. After the static mechanical properties were determined, the fatigue strength was investigated in a pulsating machine with a load ratio of R = 0. Wöhler curves were plotted and the parameters for determining the fatigue life (of' and b) were calculated.
Ključne besede: powder metallurgy, fatigue, S-N curve
Objavljeno: 16.03.2017; Ogledov: 13; Prenosov: 0
.pdf Polno besedilo (157,94 KB)

DSC/TG of Al-based alloyed powders for p/m applications
Borivoj Šuštaršič, Jože Medved, Srečko Glodež, Marko Šori, Albert Korošec, 2014, izvirni znanstveni članek

Opis: Al-based alloyed powders, appropriate for the sintering procedure (powder metallurgy, P/M) contain the alloying elements with a high solid solubility in Al, enabling reaction and liquid-phase sintering. They are surface oxidised because of a high affinity of Al to oxygen. Besides, this type of powders contains a polymeric lubricant (wax), which reduces the friction on die walls during automatic die compaction into the final compact shape of a product. This lubricant has to be removed slowly during the first stage of sintering in order to prevent deformations and cracking of the product. Consequently, its sintering is very complex. Generally, these powders are sintered in pure nitrogen with a low dew point. The optimum sintering conditions are generally determined on the basis of light and scanning electron microscopy. The investigation can also be completed very successively with differential scanning calorimetry and thermo gravimetry. The first one allows an insight into the endo- and exothermic reactions, taking place during the heating and cooling of a compacted metal powder, and the second one allows an insight into the processes, connected with the mass loss (a reduction, a lubricant removal, etc.) or mass increase (an oxidation). The DSC/TG of three commercial Al-based alloyed powders was performed in the frame of our investigations. The results were compared with the theoretical thermodynamic-based calculations and the optimum sintering conditions were proposed.
Ključne besede: aluminium powders, sintering, differential scanning calorimetry and thermo gravimetry
Objavljeno: 15.03.2017; Ogledov: 24; Prenosov: 0
.pdf Polno besedilo (319,52 KB)

Upogibna trdnost korundne keramike
Milan Ambrožič, Lovro Gorjan, 2012, strokovni članek

Opis: Statistično smo ovrednotili 5100 eksperimentalnih vrednosti upogibnih trdnosti testnih vzorcev iz redne proizvodnje korundnih keramičnih izdelkov. Primerjali smo teoretično izračunano Weibullovo porazdelitev z dvema drugima pogosto uporabljenima dvoparametričnima porazdelitvama, normalno in log-normalno, da bi ugotovili, katera se najbolj sklada z meritvami. Za izračun ustreznih prostih parametrov smo uporabili metodo največje verjetnosti (maximum-likelihood method). Potem smo za primerjavo rezultatov uporabili Q–Q-diagrame. Potrdili smo domnevo, da se z eksperimentalnimi vrednostmi trdnosti najbolj ujema Weibullova porazdelitev.
Ključne besede: upogibna trdnost, Weibullova porazdelitev, statistične metode
Objavljeno: 14.03.2017; Ogledov: 24; Prenosov: 0
.pdf Polno besedilo (238,17 KB)

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