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ABSTRACT: This paper presents two special kinds of internal oxidation phenomenon that can take place in pure metals containing a high
concentration of non-equilibrium defects. These processes are Internal Oxidation (IO) and Internal Carbonisation (IC). Both
processes start with the dissolution of oxidant (O or C) into the pure metal at the free surfaces, and continue with the diffusion
of oxidant atoms into the metal matrix volume, where they are trapped at numerous defects within the crystal lattice. Increasing
oxidant activity at these places causes local oxidation of the matrix and, consequently, precipitation of fine oxide or graphite
particles. The IO and IC processes were tested on the rapidly solidified pure copper which was produced by the Chill-Block
Melt Spinning Technique. Analysis of the IO process showed the formation of Cu-Cu2O, and the formation of Cu-C composite from the IC process.
Metals and Materials International 04/2012; 15(2):259-264. · 1.18 Impact Factor
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ABSTRACT: The paper presents the viscoplastic phenomena observed during the rotational friction-welding process of high-speed steel
M2 (AISI SAE) with carbon steel 1060 (AISI SAE). The structure, phase composition and distribution of the carbide phase in
the friction plane and adjoining zones are examined by using optical microscopy (OM) with a system for quantitative analysis,
and scanning electron microscopy (SEM) in addition to EDS analysis. The experimentally-checked mathematical relationship is
suggested for the calculation of the radial movements of the carbide phase, immediately next to the friction plane. On the
basis of qualitative and quantitative evaluation of the microstructural and rheological appearances, a model of carbide phase
distribution is also established in the viscoplastic and viscous layers in the area of the friction plane.
Metals and Materials International 04/2012; 15(5):831-841. · 1.18 Impact Factor
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ABSTRACT: Legure sa memorisanim oblikom (LMO) sastavljene od nikla i titanijuma (Ni-Ti LMO) predstavljaju nove atraktivne biomaterijale koji se mogu koristiti za izradu medicinskih sredstava. Međutim, biokompatibilnost Ni-Ti LMO često nije zadovoljavajuća, usled problema sa mikrostrukturom njihove površine. U ovom radu smo primenili novu tehnologiju izrade, koja uključuje brzo otvrdnjavanje Ni-Ti LMO valjanjem njegove rastopine, i ispitali površinu ovakve legure Auger-elektronskom mikroskopijom, fotoelektronskom spektroskopijom H-zracima i skenirajućom elektronskom mikroskopijom. Biokompatibilnost pripremljenih Ni-Ti LMO traka, kao i njihova imunomodulatorna svojstva su ispitivani na modelu humanih dendritskih ćelija monocitnog porekla (MoDĆ). Pokazali smo da brzo stvrdnjavanje Ni-Ti LMO omogućava stvaranje homogenog i tankog sloja oksida na površini, čime je poboljšana rezistentost na koroziju i smanjena citotoksičnost ovih legura u kulturi sa MoDĆ. Ni-Ti LMO trake stimulišu sazrevanje MoDĆ, što je zaključeno na osnovu promena u morfologiji ovih ćelija i povećanom ispoljavanju HLA-DR, CD86, CD40 i CD83 molekula. Međutim, Ni-Ti LMO trake stimulišu tolerogena svojstva nezrelih MoDĆ, koje sada produkuju više IL-10, IL-27 i indukuju diferencijaciju IL-10- i TGF-β-produkujućih CD4+ T ćelija. Suprotno tome, u prisustvu lipopolisaharida, kao snažnog proinflamatornog molekula, Ni-Ti LMO trake stimulišu alostimulatornu i Th1 polarizacionu sposobnost MoDĆ, dok je produkcija Th2 i Th17 citokina u kokulturi sa CD4+ T limfocitima inhibirana. Na osnovu ove studije je zaključeno da Ni-Ti LMO trake značajno modulišu funkcije MoDĆ. Ovi nalazi mogu imati vrlo značajne kliničke implikacije, jer medicinska sredstva izrađena od Ni-Ti LMO mogu izazvati i poželjne i nepoželjne efekte modulacijom imunskog sistema, što zavisi od drugih stimulusa prisutnih u mikrosredini oko implantata. (rad je objavljen u časopisu: European Cells & Materials (2012)23:58-80)
Svetski Dan Imunologije 2012; 04/2012
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ABSTRACT: Legure sa memorisanim oblikom (LMO) sastavljene od nikla i titanijuma (Ni-Ti LMO) predstavljaju nove atraktivne biomaterijale koji se mogu koristiti za izradu medicinskih sredstava. Međutim, biokompatibilnost Ni-Ti LMO često nije zadovoljavajuća, usled problema sa mikrostrukturom njihove površine. U ovom radu smo primenili novu tehnologiju izrade, koja uključuje brzo otvrdnjavanje Ni-Ti LMO valjanjem njegove rastopine, i ispitali površinu ovakve legure Auger-elektronskom mikroskopijom, fotoelektronskom spektroskopijom H-zracima i skenirajućom elektronskom mikroskopijom. Biokompatibilnost pripremljenih Ni-Ti LMO traka, kao i njihova imunomodulatorna svojstva su ispitivani na modelu humanih dendritskih ćelija monocitnog porekla (MoDĆ). Pokazali smo da brzo stvrdnjavanje Ni-Ti LMO omogućava stvaranje homogenog i tankog sloja oksida na površini, čime je poboljšana rezistentost na koroziju i smanjena citotoksičnost ovih legura u kulturi sa MoDĆ. Ni-Ti LMO trake stimulišu sazrevanje MoDĆ, što je zaključeno na osnovu promena u morfologiji ovih ćelija i povećanom ispoljavanju HLA-DR, CD86, CD40 i CD83 molekula. Međutim, Ni-Ti LMO trake stimulišu tolerogena svojstva nezrelih MoDĆ, koje sada produkuju više IL-10, IL-27 i indukuju diferencijaciju IL-10- i TGF-β-produkujućih CD4+ T ćelija. Suprotno tome, u prisustvu lipopolisaharida, kao snažnog proinflamatornog molekula, Ni-Ti LMO trake stimulišu alostimulatornu i Th1 polarizacionu sposobnost MoDĆ, dok je produkcija Th2 i Th17 citokina u kokulturi sa CD4+ T limfocitima inhibirana. Na osnovu ove studije je zaključeno da Ni-Ti LMO trake značajno modulišu funkcije MoDĆ. Ovi nalazi mogu imati vrlo značajne kliničke implikacije, jer medicinska sredstva izrađena od Ni-Ti LMO mogu izazvati i poželjne i nepoželjne efekte modulacijom imunskog sistema, što zavisi od drugih stimulusa prisutnih u mikrosredini oko implantata.
Svetski Dan Imunologije 2012; 04/2012
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ABSTRACT: We prepared 5 different fractions of nanoparticles from the gold scrap, by using a new technology, Ultrasonic Spray Pirolysis (USP). The aim of this study was to characterize the microstructure and cytotoxicity of the nanoparticles along with their immunomodulatory properties, using Concanavaline A (ConA)-treated rat splenocytes as a model of activated immune cells. Fractions 1 and 2, composed of pure gold nanoparticles, although non-cytotoxic, reduced cellular proliferation. Fraction 2, containing particles smaller in size and lesser agglomerated than fraction 1, up- and down-regulated the production of IL-2 and IL-10, respectively, by activated splenocytes. Fraction 3, containing nanoparticles composed of Au and up to 3 at.% Cu, was non-cytotoxic, but reduced IL-2 production and cell proliferation. Fractions 4 and 5, contaminated with alloying elements from the gold scrap, were cytotoxic. The extent of cytotoxicity and subsequent reduction of cytokine production, as well as the mode of cell death, depended on their composition. In conclusion, we showed that USP enables the synthesis of gold nanoparticles, which could be suitable for various biological applications, and that ConA-treated splenocytes represent a reliable model for fast and accurate evaluation of the immunotoxicological profiles of these particles. However, it is necessary to improve this technology and investigate further some of the immunomodulatory mechanisms using more specific immunological tests.
Journal of Biomedical Nanotechnology 01/2011; · 4.22 Impact Factor
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ABSTRACT: Introduction: The most commonly used materials for prosthetic denture base are acrylic resins - polymethyl methacrylate, which has all the important physical and chemical properties. The bond between a denture base and an acrylic tooth has a significant functional value. Aim: To evaluate the influence of various procedures on bonding quality between the denture base and the artificial tooth, the measurement of gaps when connecting the tooth and the denture base using an optical or electron microscope, and evaluating the mechanical properties by compressive testing. Materials and methods: Forty eight acrylic models with bonds between acrylic teeth and prosthetic denturebases, and 12 models for compressive testing were created as the materials in this in vitro study. The acrylic models were allocated to four groups (with 12 samples) for microscopy, and three groups for compressive testing. The samples for microscopy contained denture bases with fixed, unprocessed acrylic teeth, mechanically processed acrylic teeth, chemically processed acrylic teeth, and mechanically and chemically processed acrylic teeth, respectively. The acrylic models had the same dimensions, and the surface of each model was prepared using a slow speed saw, abrasive diamond paste, and special paper grinders. A special metal cast was created for compressive testing with internal dimensions of 20 x 9 mm. The size of a gap was measured on the light inverse microscope (Nikon Epiphot 300) and pressure testing was performed on a Zwick/Roell Z010 pressure machine. Results: The average value of the gap on mechanically and chemically treated samples was 68.250 μm, which was significantly lower than the gap on the untreated samples with the average value of 103.75 μm. The compressive strength was 3200 N/mm2 on untreated samples and above 6000 N/mm2 on the mechanically and chemically treated ones. Conclusions: It can be concluded that surfaces which come into contact must be mechanically and chemically processed. Although in practice prostheses are made using mechanical tooth-base retention, larger gaps occur when compared to mechanically and chemically processed surfaces.
Stomatološki Glasnik Srbije. 01/2007;
