Recent Developments in Advanced Materials and Processes

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Authors: B.R. Jovanić, M.Ž. Sarvan
Abstract: Information sent by biological materials (plant leaves) into environment is determined by the morphology and by the physiological activity of an assembly. This information can be related to the luminescence spectra emitted by the leaf, being specific for the corresponding photosystem pigments. Such an analysis can provide an increase in our understanding of particular changes in this biological material.
Authors: I. Balać, Chak Yin Tang, Chi Pong Tsui, Da Zhu Chen, P.S. Uskoković, N. Ignjatović, Dragan P. Uskokovic
Abstract: In order to obtain more accurate properties after compaction of hydroxyapatite (HAp)/poly-L-lactide (PLLA) composite, high-resolution measurement of mechanical properties method is proposed to determine the properties of each phase separately, leading to information that are valuable for the development of new materials as well as for predictive modeling purposes. The PLLA polymer processing conditions used in hot pressing of the composite strongly influence final mechanical properties of the material in the solid state. Since the aim was to measure PLLA material properties, acceptable findings could only be made using unconstrained, cured in situ nanoindentation tests. A finite element analysis of the in situ indentation experiment was performed to determine required size of plain polymer area, needed for indentation test, which would minimize the particle influence on the matrix elastic behavior.
Authors: Ljiljana Kandić, M. Mitrić, N. Ignjatović
Abstract: Composite biomaterials based on calcium phosphate ceramic due to their high bioactivity are of interest for biological application and bone tissue repair. Structural and microstructural parameters of inorganic constituent of these materials are very important for the synthesis and characterization of composites. Quantitative and qualitative content, crystallite size of phases, as well as the degree of crystallinity have a great influence on the quality of composites, their application and bone tissue repair. X-ray diffractometry was employed to investigate the components of biocomposite materials, calcium phosphate (CaP) ceramic and poly-DL-lactide-coglycolide (DLPLG) polymer, as well as the biocomposite obtained from the mentioned components. Composite biomaterial was obtained by modified emulsion process. Using the Rietveld refinement, we analyzed CaP as an inorganic component of the composite, whence we have determined structural and microstructural properties of ceramic component of the investigated composite. The results obtained by structure refinement show that calcium phosphate ceramic materials synthesized at room temperature contain hydroxyapatite HAp as a predominant phase. The calculated Ca/P ratio is 1.667. The Rietveld analysis revealed lattice parameters a(Å)=9.4324(7) and c(Å)=6.8785(6) that are in agreement with the theoretical values.
Authors: M. Lazić, Siniša Radulović, Tamara R. Todorović, D.M. Sladić, Ž. Tešić, K.K. Andjelković
Abstract: Cytotoxic activity of four series of coordinated complexes of Zn(II) and Fe(II) with hydrazone/hydrazide ligands against HeLa and B16 cells was evaluated. The ligands N’,N'2- bis[(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide (H2L1) and N’,N'2-bis[(1E)-1-(2-pyridyl) ethylidene]propanedihydrazide (H2L2) and their Zn(II) complexes showed IC50 values in the low micromolar range, while the other ligands and complexes were less active or inactive.
Authors: Iva Pajić-Lijaković, V. Nedović, B. Bugarski
Abstract: The nonlinear dynamics of brewing yeast cell growth in porous Ca-alginate matrices is considered experimentally and theoretically. The applications of alginate matrices include the reduction of internal mass transfer resistance, minimized cell leakage and growth restriction due to interactions between matrices and cell membranes comparatively to free cell culture conditions. The effects of micro-bead diameters in the range 0.3-2.0 mm on yeast cell growth were investigated. The stochastic mathematical model from the Langevin class is proposed for the interpretation of cell growth, affected by four micro-processes: micro-environmental quality changes due to nutrient diffusion into the micro-beads, cell leakage, repulsive interactions between boundary layers around the cells themselves, which contribute to the dynamics of cell growth as a negative, nonlinear feedback restriction and random kinetics effects. Such a model is used for the prediction of the optimal diameter of micro-beads, which ensures maximal final cell concentration. The results of cell growth in alginate matrices study have indicated an optimal diameter of 0.5-0.6 mm for micro-beads. Immobilized cells in these beads were not restricted significantly by mass transfer of nutrients and by cell leakage. The highest final cell concentration value indicated the largest feed-back restriction quantified by the constitutive parameter b.
Authors: V. Djordjević-Milić, A. Djordjević, S. Dobrić, Rade Injac, D. Vučković, Karmen Stankov, V. Dragojević-Simić, Lj. Suvajdžić
Abstract: Earlier investigation of fullerenol, C60(OH)24, features, in vitro, showed that fullerenol have strong antioxidative potential. In this work, we examined the influence of fullerenol as a potential antioxidative protector on doxorubicin induced cardiotoxicity in rats. Experiments were performed on adult Wistar rats, both gender. Animals were divided into six groups, each containing eight individuals. Doxorubicin was administrated i.v. (tail vein) in single dose of 8mg/kg. Fullerenol C60(OH)24 in treated animals was administrated i.p. (in doses 50, 100, 200 mg/kg) for 30 min. before application of doxorubicin. Control group (intact animals) was given saline (1 mL/kg). One group was treated only with fullerenol (100 mg/kg i.p.). Cardiotoxicity of doxorubicin as well as cardioprotective effects of fullerenol were evaluated following the heart function monitored by ECG recording during adrenalin i.v. infusion, and pathomorphological examination of the heart tissue. These evaluations were performed on the day 2 and 7 after doxorubicin administration. Both functional and pathomorphological investigations revealed no heart damage two days after given treatments. However, on the day 7 after doxorubicin injection, changes in cardiovascular reflexes to adrenalin as well as structural damage were manifest. The time for appearance of adrenalin-induced reflex bradicardia in ECG record was significantly longer in doxorubicin treated group in comparison with the control one. Also, pathomorphological examination of the heart tissue showed vacuolization of cardiomyocites. In fullerenol pretreated groups these described changes were ameliorated and corresponded to the control values. These results suggest that fullerenol might be potential cardioprotector in doxorubicin treated individuals.
Authors: P. Jodin
Abstract: Pressure pipes may be externally damaged in different ways: corrosion or notch due to diving machines. These defects may initiate a fatigue crack, which will be first part-through, then through the thickness. This results in a weakened region of the tube, then in leak of the pressure fluid contained in the pipe. There are several ways to repair the tube: changing the portion of tube, welding of extra metal in the defect, putting a welded metal sleeve or gluing a composite sleeve. This last solution seems to be the easiest and the cheapest. The advantage is that the repairing sleeve is made on site and can be put with a given pre-tension. The work presented here is the numerical study of the fracture mechanics parameters of a part-through crack in a tube submitted to internal pressure and repaired with a composite sleeve. As there is a transfer of loading from the cracked tube to the repairing sleeve, the fracture mechanics parameters of the crack such as J-integral or opening of the crack lips will be modified. The study can be used as a design procedure for such repairing sleeves.
Authors: Misa Zrilić, Marko Rakin, Aleksandar Sedmak, R. Aleksić, Z. Cvijović, Miodrag Arsić
Abstract: Considering the conditions to which steels used for the manufacture of steam pipelines are exposed, the micromechanism of their destruction in exploitation is exclusively the ductile one. In order to make an estimation of the level of the damage that occurs in exploitation, in this paper a combined experimental and numerical procedure has been developed based on micromechanical or local approach to the fracture mechanics of metallic materials. After the analysis of the results obtained for micromechanical criterion of failure for virgin steel and that used in the steam pipeline, a proposal for prolongation of the working life of tested steel for steam pipelines until the next overhaul is given.
Authors: Kemal Delijić, V. Asanović, Dragan Radonjić
Abstract: This paper describes the general trends correlating mechanical and corrosion properties with chemical composition of some Al-Fe-Si and Al-Fe-Mn-Si alloys for foils. These Al-rich eutectic alloys based on Al-Fe-Si and Al-Fe-Mn, when roll cast and appropriately processed to give fine and regular dispersion of intemetallic particles, can provide good combinations of strength and ductility. These characteristics have been responsible for the alloy success in replacing commercially pure (CP) aluminum for applications in thin sheet and foil gauges. The objective was to obtain an opinion about the possible role of alloying elements in corrosion behavior and mechanical properties of these commercial materials produced by cold rolling of twin roll cast strips.
Authors: D.R. Sekulić, I.M. Djordjević, M.V. Gordić, Zijah Burzić, M.M. Stevanović
Abstract: Unidirectional and angle-ply carbon/epoxy laminates were gamma irradiated up to doses of 12 and 20 MGy. Composites with two different, low and high temperature epoxy matrices have been submitted to irradiation and subsequent mechanical testing. The radiation effects were studied by measuring in-plane, interalminar shear and transverse tensile strength, as well as interlaminar strain energy release rate of tested composites. The immersion of composite plate in water at 80 oC and mechanical measurements at elevated temperatures emphasized irradiation effects on mechanical properties.

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