Comparative analyses of the vascular flora of the Pčinja river gorges in Serbia and Macedonia

The study’s aim is the comparative chorologic and ecological analysis of the vascular flora of the two gorges of the Pčinja River in Serbia and Macedonia which are 27 km apart. In the two gorges 1564 taxa have been recorded, 1057 being in the upper gorge in Serbia and 1174 in the lower gorge in Macedonia. Common to both gorges are 666 taxa. Chorological spectra show that in both gorges the most abundant are Mediterranean-submediterranean plants, 32.85% being in the upper and 43.97% in the lower gorge. Differences in the studied vegetation result from a diverse participation of other floristic elements such as Central European ones that are more abundant in the upper gorge (17.05%) than in the lower gorge (10.86 %). The life-form spectrum reveals that the flora in both gorges is hemicryptophyte-therophyte in character. Both gorges belong to an enclave of a Mediterranean-submediterranean region, i.e. to its submediterranean Macedonian- Thracian province

Morphological and anatomical observations on Ranunculus auricomus L. var. biformis L. in Vlasina Lake, Serbia

R. auricomus var. biformis L. (R. binatus Kit.) grows mainly in the suburbs of Vlasina plateau beside a variety of other species and forms one part of the peat-land association. Specimens were collected from the northeast coastal flooded area of Vlasina Lake (Latitude: 42° 41' 46 N, Longitude: 22° 22' 14 E). In this study, some morphological and anatomical characteristics were investigated. Samples for anatomical analysis were prepared according to the standard methods described by Ruzin (1999) though, slightly modified (Atanackovic et al., 2012). Morphological features such as leaf, petiole, stem, and root have been described. The anatomy presented in this work form the first of its kind available in the literature about this variety found in the Vlasina Lake. Transverse sections of ground-leaf, upper-leaf, petiole, stem and root have been examined and photographed. The observed morphological and anatomical feauters showed that the species grows in these flooding conditions

Application of Minkowski layer for microalloyed alumo-silicate ceramics grains fractal analysis

Porous aluminium-silicate ceramics, modified by alloying with magnesium and microalloying with alluminium belongs to a group of advanced multifunctional ceramics materials. This multiphase solid-solid system has predominantly amorphous microstructure and micro morphology. Intergranular and interphase areas are very complex, because they represent areas, where numbered processes and interactions take place, making new boundaries and regions with fractal nature. Solid contact between grains is actually very complex configuration of microcontacts with fractal nature. Fractal analysis of intergranular microstructure has included application of Minkowski layer. This layer is in correlation with fractal dimension, and defines grains contact probability. It represents convex layer of grains contour roughness and irregularity. Considering the fractal nature of intergranular contacts, it is possible to establish correlation between material electrical properties and fractal analysis, as a tool for future correlation with microstructure characterization

Synthesis of BaFe12O19-BaTiO3 multiferroics by mechanical activation

A mixture of polycrystalline powders of Fe (70 % wt.) and BaTiO3 (30 % wt.) was ball-milled in a planetary mill under air atmosphere, for different time intervals: 60, 120, 180, 240, 300 and 360 min. During the mechanical activation, the powder was exposed to oxygen from the air, resulting in formation of iron oxides: FeO and then Fe2O3 and Fe3O4. XRD and SEM analyses of the activated powders revealed that the weight fraction of the iron oxides in the mixture and microcrystal size depend on the activation time. For the powders activated for different time intervals, average crystallite size (Dhkl), dislocation density (ρn) and average microcrystal size of BaTiO3 and Fe were determined. In order to investigate the influence of thermally induced structural changes on magnetic properties, the change of magnetic properties of the pressed activated powders during multiple heating in a magnetic field of 10KA/m was measured. Maximum magnetization of the samples was reached after heating at 620 K. Pressed powder samples were sintered at temperatures of 1100 oC and 1200 °C for 2h giving the different phase diagrams. The samples sintered at 1100 oC include BaTiO3, BaFe12O19 and BaFeO2,67 as the dominant components. The samples sintered at 1200 °C containing only two components, BaTiO3 and BaFe12O19, exhibited pronounced ferromagnetic and ferroelectric propertie

Intergranular area microalloyed aluminium-silicate ceramics fractal analysis

Porous aluminium-silicate ceramics, modified by alloying with magnesium and microalloying with alluminium belongs to a group of advanced multifunctional ceramics materials. This multiphase solid-solid system has predominantly amorphous microstructure and micro morphology. Intergranular and interphase areas are very complex, because they represent areas, where numbered processes and interactions take place, making new boundaries and regions with fractal nature. Fractal analysis of intergranular microstructure has included determination of ceramic grain fractal dimension by using Richardson method. Considering the fractal nature of intergranular contacts, it is possible to establish correlation between material electrical properties and fractal analysis, as a tool for future correlation with microstructure characterization. [Projekat Ministarstva nauke Republike Srbije, br. ON 172057 i br. III 45012

Thermal parameters defined with graph theory approach in synthetized diamonds

The Nanocrystaline diamonds are very important biomedical material with variety of applications. The experimental procedures and results have been done in the Institute of Functional Nanosystems at the University Ulm, Germany. There is an existing biocompatibility of the diamond layers, selectively improved by biomimetic 3-D patterns structuring. Based on that, we have been inspired to apply the graph theory approach in analysing and defining the physical parameters within the structure of materials structure samples. Instead the parameters values, characteristic at the samples surface, we penetrate the graphs deeply in the bulk structure. These values could be only, with some probability, distributed through the micro-structure what defines not enough precious parameters values between the micro-structure constituents, grains and pores. So, we originally applied the graph theory to get defined the physical parameters at the grains and pores levels. This novelty, in our paper, we applied for thermophysical parameters, like thermoconductiviy. By graph approach we open new frontiers in controlling and defining the processes at micro-structure relations. In this way, we can easily predict and design the structure with proposed parameters

Contribution to the knowledge of distribution of certain macrophytes, invasive and threatened species in Serbia

This paper contains a short report about new and unpublished chorological data for the following species: Hydrocharis morsus-ranae L., Bidens cernuus L., Najas marina L., Potamogeton lucens L., Schoenoplectus triqueter (L.) Palla, Cyperus rotundus L., Polypogon monspeliensis (L.) Desf. and Paspalum distichum L.. Despite the fact that this paper provides insight into the distribution of analyzed species, it could be used as a base for invasive species’ Paspalum distichum L. expanding patterns research, and as a base for reevaluation of the threatened status of Schoenoplectus triqueter (L.) Palla and Cyperus rotundus L. in Serbia

Dielectric characterization of microalloyed alumo-silicate ceramics by using linear regression model

In this paper, dielectric characterization of porous alumo-silicate ceramics, modified by alloying with magnesium and microalloying with aluminum, was investigated. Microstructure investigations have revealed non-uniform and highly porous structure with broad distribution of grain size, specifically shaped grains and high degree of agglomeration. Complex multiphase system, as active microalloyed ceramics, has specific behavior under external electrical field influence. Dielectric properties (the changes of permittivity, electrical resistivity, dielectric losses and impedance) were measured in the frequency range 20 Hz – 1 MHz. All characteristics showed nonlinear distribution and complex functional dependences because of significant nonhomogeneity of active microalloyed ceramics. Values for permittivity ranged between 140 – 430. Order of magnitude for electrical resistivity was about 106 Ωm, for impedance 104 – 108 Ω, and loss tangent had values much greater than 0.05. Mathematical model of linear regression was applied on the dielectric characterization results. Consistency with experimental data was approved, since the values for correlation coefficient r and determination coefficient r2 were obtained near value 1

Visualisation of the Interaction Between Acidithiobacillus Ferrooxidans and Oil Shale by Atomic Force Microscopy

This study visually documents the mechanical contact and interaction between the bacterial cells of two biogeocenotically different strains of Acidithiobacillus ferrooxidans (At. ferrooxidans) and oil shale containing pyrite. Atomic force microscopy (AFM) imaging was used to visualise initial interaction between the microorganisms and the surface minerals of an oil shale and to evaluate bacterial effects in the first hours of the bioleaching process. Acidithiobacillus ferrooxidans was attached to the shale surface already after 2 h, and after 48 h, numerous cells covered the surface with a biofilm. After 5 day incubation with At. ferrooxidans, AFM imaging revealed ellipsoid etched pits that represent footprints left by detached cells. Combining AFM surface imaging and leaching analysis following bacterial colonisation of oil shale layers demonstrates that an initial attachment to the surface is necessary for the leaching and that later on, once a sufficient concentration of Fe2+ ions in the solution is achieved, cells detach to become free cells, and leaching occurs primarily by the Fe3+. This experiment confirmed that microorganisms isolated from sites in which a particular substrate is found will demonstrate stronger binding to that substrate

Reconstruction of fiber reinforcement in epoxy-based composite

Polymer matrix composites (PMCs) are very attractive materials due to a possibility to achieve versatile properties by combining with ceramic or metal reinforcement in different shapes and sizes. As a result, PMCs have found application in nearly every field, from household appliances to aerospace industry. Modern microelectronic devices contain conductive polymers with fillers that enhance their electrical properties. In addition, PMCs are being used as insulators and adhesives, contributing to the long life of electronic devices. Epoxy resins are the most commonly used insulators and adhesives. In order to improve their fracture toughness, glass fibers can be used as an efficient reinforcement. However, with the purpose of designing a composite with good mechanical properties and durability, deep knowledge of microstructure is required. In addition, microstructural analysis can be used to connect shape and size of pores or reinforcement with various physical properties. Fractal nature analysis is a valuable mathematical tool that can be employed for different shapes and forms rendering. In this manner, successful design and prediction of composite’s properties could be obtained. In this research, field emission scanning electron microscopy (FESEM) images were used for fractal analysis of glass fibers, with the aim of reconstructing the shape