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Determination of the cross-linking degree of unmodified epoxy resin by cycloaliphatic polyamine and polyamidamin hardeners by ftir spectroscopy
Zlatkovi? Sa?a,Nikoli? Goran S.,StamenkoviJakov V.
Hemijska Industrija , 2003, DOI: 10.2298/hemind0311563z
Abstract: Unmodified epoxy resin GY250 was crosslinked by the cycloaliphatic polyamino hardener HY847 and polyamidamine hardener HY848 in the different mass ratios. The degree of crosslinking of the epoxy resin and the quantity of unreacted epoxy groups were determined by a spectroscopic FTIR method. The optimal time of complete crosslinking, as a criterion of the degree, was determined by measuring the film hardness indirectly (JUS H.C8.055). The optimal stoichiometric ratio of 100:18:32 (GY250:HY847:HY848) was defined by correlating parameters which directly depend on the degree of crosslinking and the period of application of the epoxy resins, as a prerequisite for forming 2-component epoxy systems which are comparatively more elastic adhesive and waterproof.
Study of the catalytic selectivity of an aqueous two-component polyurethane system by ftir spectroscopy
StamenkoviJakov V.,Caki? Suzana M.,Nikoli? Goran S.
Hemijska Industrija , 2003, DOI: 10.2298/hemind0311559s
Abstract: The difficulty in formulating a two component waterborne polyurethane, is the isocyanate-water side reaction, which can lead to gassing/foaming, loss of isocyanate functionality, low gloss and a reduced pot life. To compensate for this side reaction, these formulations usually contain a large excess of isocyanate. Tin compounds, especially dibutyltin dilaurate, are widely used in coatings as catalysts for the isocyanate/hydroxyl reaction. Because of the high aquatic toxicity of some organotin compounds, there has been an attempt to ban organotin compounds from all coating applications. As a general rule, organotin catalysts are not selective, they catalyze the reaction of isocyanates with both hydroxyl groups and water and also catalyze the hydrolysis of ester groups. One novel approach to control the water side reaction is the use of catalysts which selectively catalyze the isocyanate-polyol reaction and not the isocyanate-water reaction. The selectivity of a variety of metal catalysts (metal octoates, metal acetylacetonates and mangan chelates with mixed ligands) to catalyze the preferred reaction was measured using the FTIR method.
The influence of sodium-polyacrilic macromolecular chain length to the powder detergents secondary washing performances
Milojevi? Vladimir S.,Nikoli? Ljubi?a B.,Nikoli? Goran,StamenkoviJakov
Hemijska Industrija , 2013, DOI: 10.2298/hemind120220040m
Abstract: In order to investigate the influence of sodium-polyacrylate polymer as a co-builder in addition to the carbonate/zeolite builders in detergent builder system, secondary washing performances of powder laundry detergent containing equal percentage of sodium polyacrylate with the different weight average molar mass, Mw, have been examined. The value of the degree of whiteness, elongation at break, and total residue content are the most important secondary washing performances that significantly depend on sodium polyacrylates efficiency used as crystal inhibitors, stabilizers for suspended soil, and agents for soil redisposition prevention on fabric surface. The values of the whiteness and elongation at break for cotton fabrics increase with the increase of average weight molecular mass, Mw, up to the value of 70000 g/mol, while in the case of further increase of weight average molar mass up to the 250000 g/mol value of these characteristics begin to decline. The values of the total residue content after combustion indicate an increase in its content with the increase of weight average molar mass of 3000 to 70000 g/mol, while the highest value has been reached in the sample of detergent containing sodiumpolyacrilic with the weight average molar mass of 250000 g/mol. All detergent samples show no significant dependence of the secondary washing characteristics on the number of washing cycles.
Physico-chemical characterization of mixed-ligand complexes of Mn(III) based on the acetylacetonate and maleic acid and its hydroxylamine derivative
Caki? Suzana M.,Nikoli? Goran S.,StamenkoviJakov V.,Konstantinovi? Sandra S.
Acta Periodica Technologica , 2005, DOI: 10.2298/apt0536091c
Abstract: Two new Mn(III) mixed-ligand complexes with two acetylacetonate (acac) ligands and one maleate ligand and its hydroxylamine derivative of the general formula [Mn(C5H7O2)2L] were prepared. Their structure was established by using elemental analysis, FTIR and UV/VIS spectroscopic methods, as well as magnetic measurement. Replacement of the acetylacetonate ligand by the corresponding acid ligand has been confirmed in Mn(III) acetylacetonate. Based on the obtained experimental data and literature indications, structural formulae to these compounds were assigned.
A comment on non-Abelian duality and the strong CP problem
Jakov Pfaudler
Physics , 1997,
Abstract: It is pointed out that the strong CP problem may have a natural solution in the context of a recently proposed dualized version of the Standard Model where Higgs fields and generations emerge naturally. Although fermions have finite pole-masses, the fermionic mass matrix itself is factorizable (having only one nonzero eigenvalue) to all orders in perturbation theory thus allowing one to perform a chiral transformation $\psi\to\psi'=e^{-i\gamma_{5}\alpha}\psi$ and to rotate the theta-angle to zero.
Surgical management of macular holes-indications and complications
Stamenkovi? Miroslav
Acta Chirurgica Iugoslavica , 2012, DOI: 10.2298/aci1203085s
Abstract: Macular hole surgery is very demand surgery performed due to fullthickness macular rupture characterized by abscence of all retinal layers. Indications for surgery includes stages 3 and 4 regarding to Gass classification. Some authors sugest surgery for stage 2 but results are promissing only in anatomical reconstruction. Complications are evident such as cataract, late macular reopening, retinal tears and detachment, visual field defect etc. With improving surgical techniques, the rate of complications became lower.
Du?an Stamenkovi
Facta Universitatis Series : Linguistics and Literature , 2010,
Abstract: The paper is a contrastive study that tries to explore various metaphoric and extended uses of the verbs that are considered to be hyponyms of the generic vision verbs gledati in Serbian and look in English. These verbs, being classified as verbs of basic bodily perception, are a very likely source domain in the process of metaphorization and other forms of extended usage. The main goal of the paper is to compare the ways in which verbs denoting various kinds of visual perception shift or have shifted their primarymeanings, as well as the ways in which they get joined by other, 'non-visual' meanings in Serbian and English. It will also explore a number of typically non-visual verbs which attain visual meaning in the process of metaphorization. The verbs are divided into semantic groups and analysed one by one. Finally, the paper also tries to provide solutions to the problems which may emerge in the process of translating various meanings of these verbs from Serbian into English.
Faculty of geography, University of Belgrade: Initiator and development driving force of geograpghy and related sciences and disciplines in Serbia
Stamenkovi? Srboljub ?.
Journal of the Geographical Institute Jovan Cvijic, SASA , 2007, DOI: 10.2298/ijgi0757013s
Abstract: The Faculty of Geography is one of the 31 faculties within the University of Belgrade and with one of the longest tradition among them. It has been established in 1893 year. From the early beginnings up to day, it is the biggest and the most significant geographic institution (by scope and diversity of education programs, by the number of teachers, associates, researchers and realized scientific results) in Serbia, as well as in Balkans, south Eastern Europe, and it could be freely said, in a global scale. In all the phases of his existence, Faculty of Geography is the initiator and driving force of, first of all, scientific and scholar geography and then tourismology, spatial planning, demography and rudiments of geospatial in environment. New scientific ideas and concepts have been developed in Belgrade and then they have been transmitted to the other University centers and geographic institutions in Serbia and neighboring countries.
Jakov Pranji?,Josip Mesec
Rudarsko-Geolo?ko-Naftni Zbornik , 1992,
Abstract: The paper analyses possibilities of revitalization of ruined areas having specific hydrologic, geologic, climatic and soil factors. A plan for sanation with autochtonous and allochtonous plants is described. Preparatory and planting techniques and general distribution of plants correspond to the conditions and state of the quarry after closure.
Transport coefficients in non-quasiparticle systems
Jakovác A.
EPJ Web of Conferences , 2011, DOI: 10.1051/epjconf/20111306004
Abstract: Transport coefficients, in particular the shear viscosity to entropy density ratio are studied in systems where the small-width quasiparticle assumption is not valid. It is found that η/s has no universal lower bound, the minimal value depends on the system and the temperature, and can be even zero. We construct models where the 1/4π conjectured bound is violated.
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