Current Research in Advanced Materials and Processes

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Authors: D. Božić, M. Vilotijević, V. Rajković, Ž. Gnjidić
Abstract: The compressive characteristics and fracture behavior of CW67 aluminum alloy and of a composite based on CW67 alloy were studied under unaxial compressive loading in the temperature range 25-400°C, at a constant strain rate of 1 - 3 10 4 . 2 s × . The yield strength values of the composite were higher than those of the monolithic alloy at all temperatures. The ultimate strength values of the composite were lower at room temperature, but higher at elevated temperatures when compared with those of the monolithic alloy. The composite exhibited lower ductility than the monolithic alloy in the entire temperature range. High concentration of SiC particles in the structure of CW67 composite affected its compressive properties. At higher temperatures, it behaved like a typical precipitation hardened alloy, in other words, with temperature increase the main influence on the mechanical properties occurred in its matrix. When temperature rises, the fracture process changes from particle cracking and particle agglomerate decohesion (at room temperature) to particle matrix debonding (at high temperature).
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Authors: V. Rajković, D. Božić, D. Vračarić, E. Romhanji
Abstract: Prealloyed copper powder containing 2.5wt. %Al was processed in a planetary ball mill to evaluate matrix hardening due to formation of Al2O3 particles in situ by internal oxidation. After milling, the powders were heat treated in hydrogen in order to reduce copper oxide formed on particle surfaces during milling. The compacts were made by hot pressing. The examinations show that the compacts possess a good combination of high strength and high electrical conductivities. After 5h of milling the microhardness of the prealloyed compact was 3 to 4 times higher than that of the as-received electrolytic copper compacted under the same conditions, while the conductivity was 68% IACS. Also, it was found that the prealloyed compacts preserved much of the hardness after exposure to high temperature in inert atmospheres.
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Authors: Aldo Roberto Boccaccini, J.J. Blaker, V. Maquet, R. Jerome, S. Blacher, Judith A. Roether
Abstract: Porous bioresorbable and bioactive composite materials designed for applications as scaffolds in tissue engineering are discussed. The systems fabricated by thermally induced phase separation method and based on poly(D,L-lactide) (PDLLA) or poly(lactic acid-co-glycolic acid) (PLGA) with additions of bioactive glass particles (45S5 Bioglass®) are described in detail. The scaffolds exhibit a well-defined, oriented and interconnected porosity. The porosity structure of foams with and without Bioglass® was characterised by scanning electron microscopy. The in vitro bioactivity and degradability of the composite foams were investigated in contact with phosphate buffer saline (PBS) and simulated body fluid (SBF). High chemical reactivity of scaffolds in SBF, which leads to the prompt formation of bonelike hydroxyapatite crystals on the material surfaces, indicates an enhanced bioactive character of the composites and therefore their potential for use as bone tissue engineering scaffolds.
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Authors: G. Keković, D. Raković, M.V. Satarić, Dj. Koruga
Abstract: Contemporary trends in science and technology are characterized by integration of biological and technical systems, like in nanotechnology, nanobiology, and quantum medicine. In our case, we were motivated by a necessity to understand charge transport through microtubular cytoskeleton as a constitutive part of acupuncture system. The high frequency component of acupuncture currents, widely exploited in microwave resonance stimulation of acupuncture system in the past decade, implies that explanation of the cytoplasmatic conductivity should be sought in the framework of Frohlich theory. Accordingly, in this paper we critically analyze the problem of the microwave coherent longitudinal electrical oscillations as a theoretical basis for understanding soliton phenomena in microtubules, showing that charged kink-soliton nonlinear microtubular excitations might be a good candidate for charge transport in microtubules.
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Authors: D. Raković, M. Dugić, M.B. Plavšić
Abstract: In this paper we describe the biopolymer chain folding problem in the framework of the so-called quantum decoherence theory. As we propose a rather qualitative scenario yet bearing generality, it seems this provides promising basis for the solution-in-principle of the (semi) classically hard kinetic problem of biopolymer chain folding from coiled to native conformation in highly selective ligand proteins/target-receptors biomolecular recognition processes, implying underlying macroscopic quantum nonlocality on the level of biological cell.
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Authors: N. Ignjatović, P. Ninkov, Z. Ajduković, V. Konstantinović, Dragan P. Uskokovic
Abstract: Composite biomaterials, like calciumphosphate/bioresorbable polymer, offer excellent potential for reconstruction and reparation of bone tissue defects induced by different sources. In this paper synthesis of calciumphosphate/poly-DL-lactide-co-glycolide (BCP/DLPLG) composite biomaterial formed as filler and blocks was studied. BCP/DLPLG composite biomaterial was produced in the form of spherical granules of BCP covered by a DLPLG layer, average diameter of 150-250 µm. By cold and hot pressing of granules at up to 10000 kg/cm2, blocks with fine distribution of phases and porosity up to 3% were obtained. Characterization was performed by wide-angle X-ray structural analysis (WAXS), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), infrared spectroscopy (IR), and mechanical properties by defining the compressive strength. In vitro citotoxicity research was carried out on cellular cultures of fibroblasts of human (MRC5) and mouse (L929). In vivo research was performed in two steps. Reparatory ability of BCP/DLPLG in mice was examined in the first step, and then bone tissue reconstruction possibilities on 10 patients in the next step. In vitro tests showed very good fibroblast adhesion and non-citotoxicity of the composite. A material is considered non-cytotoxic if the cell survival is above 50 %, and in our case it was 90%. In vivo research on mice indicated high level of reparatory ability of this composite with formation of new bone and vascular tissue six weeks after reparation. Application of this composite for healing infrabone defects of patients showed a high level of osseous regeneration.
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Authors: D. Bugarski, B. Obradović, M. Petakov, G. Jovčić, N. Stojanović, B. Bugarski
Abstract: Alginate is currently being employed and explored for a broad range of biomedical and biotechnology applications, due to its biodegradability and simple procedure for cell immobilization. However, cell immobilization was mostly aimed for immunoisolatory and biochemical processing applications and far less is known about potentials of alginate as a substrate for tissue formation. In the present work, isolation, immobilization and cultivation procedures of murine bone marrow stromal cells (BMSC) were studied and standardized in order to establish the alginate-bioreactor culture system for chondrogenic and/or hematopoiesis-supportive tissue progression. Two techniques for cell immobilization based on alginate were investigated: entrapment within gel matrix using electrostatic droplet generation and simple cell adsorption onto gel surfaces. Alginate gels in forms of microbeads and discs with immobilized culture expanded BMSC were cultivated for up to 30 days and analyzed for surface properties, cell concentration, viability, and differentiation.
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Authors: B. Obradović, B. Bugarski, Z. Todosijević, V. Nedović, D. Bugarski, G. Vunjak-Novaković
Abstract: Alginate is one of the mostly used hydrogels for cell entrapment aimed for applications in food industry, environmental engineering, pharmacy and biomedicine. One of the major parameters affecting cell viability and activity is cell distribution inside the immobilization matrix. In addition, changes in cell distribution over the cultivation time could indicate mass transfer limitations, favorable local environments or cell differentiation. In this study, immobilization and distribution of brewing yeast in alginate microbeads were investigated as a model system of colony forming cell growth. Cell distributions were attained by image analysis of histological cross sections of microbeads used in beer fermentation. A mathematical model based on cellular automata approach was developed for three-dimensional simulations of cell arrangement over the fermentation time.
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Authors: M. Radić, N. Ignjatović, Zoran Nedić, M. Mitrić, Dejan Miličević, Dragan P. Uskokovic
Abstract: In this paper we report the results on synthesis of a composite biomaterial based on biphasic calcium phosphate (BCP) and poly-(DL-lactide-co-glycolide) (DLPLG). Besides, we have investigated the influence of new synthesis method on the structure and characteristics of the composite. The synthesis of biphasic calcium phosphate from Ca(NO3)2 x 4H2O and (NH4)3 PO4 in alkali environment was performed by means of precipitation technique. Composite material BCP/DLPLG was first prepared from commercial granules using chemical methods. Powdered polymer DLPLG was then homogenized at appropriate ratio with addition of biphasic calcium phosphate into the suspension. All samples were characterized by DSC, IR, X-Ray and SEM techniques.
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Authors: V. Kojić, D. Jakimov, G. Bogdanović, A. Djordjević
Abstract: The aims of this paper were to investigate cell growth activity of fullerenol C60(OH)24, its modulating effect on antitumor drug-induced cytotoxicity, and genotoxic influence of fullerenol at nanomolar concentrations. Human breast cancer cell lines, MCF-7 and MDA-MB-231, were treated with fullerenol at concentrations from 0.9 to 3.9 µg/ml alone or simultaneously with antitumor drugs (doxorubicin, cisplatin, taxol, and tiazofurin; IC50 concentrations) for 2 hours. Growth inhibition was evaluated by colorimetric SRB assay after recovery period of 24, 48, and 96 hours. The genotoxic examination was performed using sister chromatid exchange test and micronucleus assay, at fullerenol concentration ranging from 1 to 5 µg/ml. The fullerenol alone mildly inhibits the growth of both cell lines. Simultaneous administration of fullerenol and antitumor drugs strongly suppressed antitumor drug-induced cytotoxicity. The rate of cytotoxicity inhibition depended on fullerenol concentration, type of antitumor drug and cell line. Protection against doxorubicin and cisplatin was more pronounced than against taxol and tiazofurin. Fullerenol was not found to be genotoxic to investigated cell lines.
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