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Search Results: 1 - 10 of 306 matches for " Mirkovi? Nemanja "
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Effect of recasting on the elastic modulus of metal-ceramic systems from nickel-chromium and cobalt-chromium alloys
MirkoviNemanja
Vojnosanitetski Pregled , 2007, DOI: 10.2298/vsp0707469m
Abstract: Background/Aim. Elastic modulus of metal-ceramic systems determines their flexural strength and prevents damages on ceramics during mastication. Recycling of basic alloys is often a clinical practice, despite the possible effects on the quality of the future metal-ceramic dentures. This research was done to establish recasting effects of nickel-chromium and cobalt-chromium alloys on the elastic modulus of metalceramic systems in making fixed partial dentures. Methods. The research was performed as an experimental study. Six metal-ceramic samples of nickel-chromium alloy (Wiron 99) and cobalt-chromium alloy (Wirobond C) were made. Alloy residues were recycled through twelve casting generations with the addition of 50% of new alloy on the occasion of every recasting. Three- point bending test was used to determine elastic modulus, recommended by the standard ISO 9693:1999. Fracture load for damaging ceramic layer was recorded on the universal testing machine (Zwick, type 1464), with the speed of 0,05 mm/min. Results. The results of this research revealed significant differences between elasticity modules of metal-ceramic samples in every examined recycle generation. Recasting had negative effect on the elastic modulus of the examined alloys. This research showed the slight linear reduction of elastic modulus up to the 6th generation of recycling. After the 6th recycling there was a sudden fall of elastic modulus. Conclusion. Recasting of nickelchromium and cobalt-chromium alloys is not recommended because of the reduced elastic modulus of these alloys. Instead of reusing previously recasted alloys, the alloy residues should be returned to the manufacturer. .
Mechanical properties of metal-ceramic systems from nickel-chromium and cobalt-chromium alloys
MirkoviNemanja
Vojnosanitetski Pregled , 2007, DOI: 10.2298/vsp0704241m
Abstract: Background/Aim. Metal-ceramic bond strength and alloys' elastic modulus clearly determine the potential of alloy application, because the ceramic integrity during mastication depends on these two characteristics. The aim of this study was to evaluate metal-ceramic bond strength and elastic modulus of cobalt-chromium alloys in making porcelainfused- to-metal restorations, regarding the application of the most frequent nickel-chromium alloy. Methods. The research was performed as an experimental study. Six metalceramic samples were made from nickel-chromium alloy (Wiron 99) and cobalt-chromium alloy (Wirobond C), according to the manufactures manuals and instructions from ISO 9693: 1996. Three-point bending test was performed up to the ceramic fracture. The fracture load was measured on an universal testing machine (Zwick, type 1464), with cross-head speed of 0,05mm/min. Results. The results of this study confirmed the significant differences between the metal-ceramic bond strength (p < 0.01) and elastic modulus (p < 0.001) of nickel-chromium and cobalt-chromium alloys, where cobalt-chromium alloys showed higher values for both tested parameters. Conclusion. Cobalt-chromium metal-ceramic alloys can successfully replace nickel-chromium alloys, especially for fabrication of long-span metal-ceramic bridges due to the great flexural strength.
Fracture toughness of zirconia ceramic crowns made by feather-edge tooth preparation design
MirkoviNemanja,?padijer-Gostovi? Aleksandra,Lazi? Zoran,Trifkovi? Branka
Vojnosanitetski Pregled , 2012, DOI: 10.2298/vsp100820004m
Abstract: Background/Aim. Fracture toughness determines functional crown strenght and prevents damages on ceramics during mastication. There is a lack of relevant literature data about fracture toughness of crowns made by feather-edge preparation. Mechanical testing of ceramic samples is supposed to show if feather-edge tooth preparation is a successful method for making ceramic crowns without any risk of reduction of their mechanical properties. This research was done to establish effects of feather-edge tooth preparation on fracture toughness of single zirconia ceramic crowns. Methods. The research was performed as an experimental study. Sixty (60) ceramic crowns were made on non-carious extracted human premolars. Thirty (30) crowns were made on the basis of feather-edge preparation (experimental group I). The group II included 30 crowns made on 1 mm rounded shoulder. Crowns fabrication was executed on a copy mill production system “Zirkonzahn” (Zirkonzahn GMBH, Gais, Germany). The spherical compression test was used to determine fracture toughness, using 6 mm diameter ceramic ball. Fracture load for damaging ceramic crown was recorded on a universal testing machine - Zwick, type 1464, with the speed of 0.05 mm/min. Results. The results of this research introduced significant differences between fracture toughness of ceramic samples in every examined group. However, fracture toughness of crowns from both group was above 2 000 N, what was double beyond a recommended value. The mean value of fracture toughness in the feather-edge group was 2 090 N, and in shoulder group it was 2 214 N. Conclusion. This research showed a high fracture toughness of zirconia crowns made on feather-edge preparation. The examined crowns showed a fracture resistance at a sufficient distance in relation to the minimum values of functional loads. Further research of functional loads of these crown is necessary, as well as research of marginal adaptation of cemented crowns and gingival inflammatory response.
Effect of recasting on the thickness of metal-ceramic interface of nickel-chromium and cobalt-chromium alloys
MirkoviNemanja,Draganjac Miroslav,Stamenkovi? Dragoslav,Risti? Ljubi?a
Vojnosanitetski Pregled , 2008, DOI: 10.2298/vsp0805365m
Abstract: Introduction/Aim. This research was done to establish recasting effects of nickel-chromium and cobalt-chromium alloys on the thickness of their metal-ceramic interface in making fixed partial dentures. Metal-ceramic interface determines their functional integrity and prevents damages on ceramics during mastication. Investigation of metal-ceramic samples is supposed to show if base metal alloys for metalceramics are successfully recycled without any risk of reduction of metal-ceramic interface thickness. Methods. The research was performed as an experimental study. Per six metal-ceramic samples of nickel-chromium alloy (Wiron99) and cobalt-chromium alloy (Wirobond C) were made each. Alloy residues were recycled through twelve casting generations with the addition of 50% of new alloy on the occasion of every recasting. Analysis Energy Dispersive X-ray (EDX) (Oxford Instruments) and Scanning Electon Microscop (SEM) analysis (JEOL) were used to determine thickness of metal-ceramic interface together with PC Software for quantification of visual information's (KVI POPOVAC). Results. Results of this research introduced significant differences between thickness of metal-ceramic interface in every examined recycle generation. Recasting had negative effect on thickness of metal-ceramic interface of the examined alloys. This research showed almost linear reduction of elastic modulus up to the 12th generation of recycling. Conclusion. Recasting of nickel-chromium and cobaltchromium alloys is not recommended because of reduced thickness of metal-ceramic interface of these alloys. Instead of recycling, the alloy residues should be returned to the manufacturers.
Active substances in medicinal plants with application in stomatology
Mirkovi? Silvija
Stomatolo?ki Glasnik Srbije , 2002, DOI: 10.2298/sgs0204101m
Abstract: The purpose of this work was to present chemical structure and basic characteristics of some active substances in medical plants which are used in stomatology. Considering their chemical content and pharmacological effects, all active substances of herbal origin are divided in four groups tannins, flavonoids, aetheric oils and the group of herbal species which show immunostimulating effect. Tannins are active substances of medical plants whose function are primarily based on precipitation of proteins and are used for disinfection of skin and oral mucose as well as for haemostatic purposes. Flavonoids are herbal pigments. They work as diuretics, and in dentistry they could be used as antiinflammatory agents. Essential oils are part of herbal species and are used as korigens of taste and smell. For their antiseptic and disinfective effects, essential oils are used in dentistry as preparations like toothpastes, mouth wash and chewing-gums. Immunostimulators of herbal origin are especially interesting in the decreasing immunity treatment for their slight toxic characteristics.
USE OF WEBSITES FOR MARKETING AND DISTRIBUTIVE PURPOSES BY INSURANCE COMPANIES IN OUR COUNTRY AND AROUND THE WORLD
Vasilijana Mirkovi
Zbornik Radova Ekonomskog Fakulteta u Isto?nom Sarajevu , 2012,
Abstract: The development andcommercialization of the Internet was followed bythe birth of numerous web presentations oforganizations involved in various businessactivities. After 1996, the use of Internet-connectedapplications has intensified in the field ofinsurance. Since then, an increasing number ofinsurance companies have used web sites, primarilyfor marketing purposes. This paper attempts toclassify the basic types of web sites for insurancecompanies and give the specific examples. Itprovides a detailed analysis of the degree of use ofelectronic forms for marketing and distributivepurposes, with special reference to practice inBosnia and Herzegovina, Serbia and Croatia. Theresearch shows that many countries exhibit aprogressive tendency toward the increased use ofweb presentations of insurance companies for theaforementioned purposes. The final part of thepaper highlights the factors that have contributedto the introduction of web business model intoinsurance companies’ strategies in many countriesthroughout the world, including the growingnumber of domestic insurers as well.
Civil engineering projects realization management
Mirkovi? Slobodan
Facta Universitatis Series : Architecture and Civil Engineering , 2006, DOI: 10.2298/fuace0602085m
Abstract: The paper treats the management of the realization of civil engineering projects or civil engineering buildings construction management, as a complex dynamic process, which entails a large number of strategic and operative decisions which are important for an efficient, cost effective, and economic construction. The management process execution is not possible without the functions such as planning, organizing, coordination and control. Planning as the initial function, important for the forecast of the future events tasks and goals, is rendered much simpler by the application of computers and software packages. Such software packages facilitate the integral management planning, realization, as well as control of the course of realization of civil engineering projects, that is the entire course of civil engineering buildings construction. The most frequent programs in this application are the Scheduler, Prima Vera and Project. The experience acquired in the application of these software packages has shown that the best results in civil engineering have been attained by the software package PROJECT 2003.
Challenging the Cosmological Constant
Kaloper, Nemanja
High Energy Physics - Phenomenology , 2007, DOI: 10.1016/j.physletb.2007.07.061
Abstract: We outline a dynamical dark energy scenario whose signatures may be simultaneously tested by astronomical observations and laboratory experiments. The dark energy is a field with slightly sub-gravitational couplings to matter, a logarithmic self-interaction potential with a scale tuned to $\sim 10^{-3} {\rm eV}$, as is usual in quintessence models, and an effective mass $m_\phi$ influenced by the environmental energy density. Its forces may be suppressed just below the current bounds by the chameleon-like mimicry, whereby only outer layers of mass distributions, of thickness $1/m_\phi$, give off appreciable long range forces. After inflation and reheating, the field is relativistic, and attains a Planckian expectation value before Hubble friction freezes it. This can make gravity in space slightly stronger than on Earth. During the matter era, interactions with nonrelativistic matter dig a minimum close to the Planck scale. However, due to its sub-gravitational matter couplings the field will linger away from this minimum until the matter energy density dips below $\sim 10^{-12} {\rm eV}^4$. Then it starts to roll to the minimum, driving a period of cosmic acceleration. Among the signatures of this scenario may be dark energy equation of state $w \ne -1$, stronger gravity in dilute mediums, that may influence BBN and appear as an excess of dark matter, and sub-millimeter corrections to Newton's law, close to the present laboratory limits.
A New Dimension Hidden in the Shadow of a Wall
Kaloper, Nemanja
High Energy Physics - Phenomenology , 2007, DOI: 10.1016/j.physletb.2007.06.054
Abstract: We propose a new way to hide the fifth dimension, and to modify gravity in the far infra-red. A gravitating tensional membrane in five dimensions folds the transverse space into a truncated cone, stoppered by the membrane. For near-critical tension, the conical opening is tiny, and the space becomes a very narrow conical sliver. A very long section, of length comparable to the membrane radius divided by the remaining conical angle, of this sliver is well approximated by a narrow cylinder ending on the membrane. Inside this cylindrical throat we can reduce the theory on the circle. At distances between the circle radius and the length of the cylinder, the theory looks 4D, with a Brans-Dicke-like gravity, and a preferred direction, while at larger distances the cone opens up and the theory turns 5D. The gravitational light scalar in the throat can get an effective local mass term from the interplay of matter interactions and quantum effective potentials on the cone, which may suppress its long range effects. We discuss some phenomenologically interesting consequences.
Hollywood industry: Correlation between film production and political discourse
Zvijer Nemanja
Sociologija , 2005, DOI: 10.2298/soc0501045z
Abstract: The paper focuses on the relation between Hollywood industry and political establishment of the USA, particularly US foreign policy and the military intervention as its specific form. Only the biggest and the most significant US military interventions were considered: World War Two, Korean War, Vietnam War, military interventions in Latin America, in the Middle East, Asia, Africa and on Balkan, concerning their treatment in Hollywood movies without analyzing them in broader socio-political context. In addition, the anticommunism in Hollywood is also considered, which was perhaps the most perennial content of the US foreign policy.
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