Electrical properties of ZnO varistors prepared by direct mixing of constituent phases

Varistor samples containing different amounts of constituent phases were prepared by direct mixing of constituent phases. Detailed electrical characterization was performed to explain the influence of minor phases (spinel and intergranular phases) on overall properties. Characterization included investigation of the non-linear coefficients (α), breakdown electric field (EB), leakage currents (JL), grain boundary barrier hight (ΦB) and constant β from current-voltage characteristics, as well as calculation of activation energies for conduction (EA) from ac impedance spectroscopy in the temperature interval 30-410°C. Varistors sintered at 1100 °C for 1 h showed pronounced differences in electrical properties depending on relative molar ratios of the phases. Results were discussed in the sense of possible reduction of the content of minor phases in ZnO varistors

Electrical properties of mechanically activated zinc oxide

Microstructural properties of a commercial zinc oxide powder were modified by mechanical activation in a high-energy vibro-mill. The obtained powders were dry pressed and sintered at 1100°C for 2 h. The electrical properties of grain boundaries of obtained ZnO ceramics were studied using an ac impedance analyzer. For that purpose, the ac electrical response was measured in the temperature range from 23 to 240°C in order to determine the resistance and capacitance of grain boundaries. The activation energies of conduction were obtained using an Arrhenius equation. Donor densities were calculated from Mott-Schottky measurements. The influence of microstructure, types and concentrations of defects on electrical properties was discussed

Strategije psihološke odbrane od straha od smrti

In the present study, we set out to explore the psychological strategies engaged to defend oneself from the basic existential insight: the one of the inevitable personal mortality. We wished to examine how young individuals reacted to reminders of mortality and whether these reactions were also related to the socio-cultural context and the important groups they identify with. For these goals, we applied the framework of Terror management theory proposing that people achieve protection from a potentially paralysing fear of death through investing in valued worldviews and maintaining a positive image of themselves as part of these worldviews. Individuals who believe that they are an important part of a meaningful universe can achieve a symbolic transcendence of their inherently mortal nature. We investigated the psychological strategies of defence in a series of five experiments, with a total of 465 participants. After subtle reminders of personal mortality, we investigated whether participants would engage in intensified efforts to enhance and protect the collective self-image stemming from identification with an important group (i.e. the ethnic group; Experiment II) or the individual self-image (Experiment III and IV). We also explored whether the preference for individual vs. collective enhancement would depend on personal value orientations, i.e. the level of individualism/ collectivism of the participants (Experiment V). To provide a more stringent test of the basic tenets of the theory, we compared the effects of mortality reminders to reminders of other existential concerns (i.e. life uncertainty), as well as more everyday concerns of the participants (i.e. exam anxiety). We also investigated the cognitive and affective mediating processes...U aktuelnoj studiji želeli smo da istražimo strategije psihološke odbrane kojima se ljudi služe prilikom suočavanja sa osnovnim egzistencijalnim uvidom: o neizbežnosti lične smrtnosti. Želeli smo da ispitamo kako mlade osobe reaguju na podsetnike na vlastitu smrtnost i da li su ove reakcije povezane sa socio-kulturnim kontekstom i značajnim grupama sa kojima se identifikuju. U ovom cilju, sagledali smo istraživački problem u okvirima teorije upravljanja strahom, koja pretpostavlja da ljudi postižu zaštitu od potencijalno parališućeg straha od smrti kroz ulaganje u vrednovane poglede na svet i očuvanje pozitivne slike o sebi samima, kao delu tih svetova. Osoba koja veruje da je značajan deo smislenog univerzuma, time postiže simboličku transcendenciju vlastite smrtne prirode..

Chemical Stability of Doped BaCe0.9Y0.1O3-x as a Proton Conducting Electrolyte for IT-SOFC

BaCe0.9Y0.1O3-δ (BCY) has been one of the most studied materials known for its highest proton conductivity at temperatures between 500 and 700 ºC, which allows its application as a proton conducting electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFC). The proton conductivity is an exclusive property of mixed oxides with perovskite structure and large unit cell volume, such as BaCeO3 or SrCeO3. Doping with aliovalent cations (Y3+) that replace Ce4+ induces formation of point defects (oxygen vacancies), which in wet or hydrogen containing atmosphere allow proton mobility. The main disadvantage of this material is its instability in CO2-rich atmosphere due to the basic character of the crystal lattice, thus limiting its application in SOFCs in respect to fuel selection. However, the stability of BCY can be enhanced by doping with cations that may raise the acidic character of the material, such as Nb5+, Ta5+ or In3+. Introduction of pentivalent cations will lead to reduced amount of point defects and consequently lower proton conductivity and it is therefore recommended that their molar concentration should not exceed 5 %. On the other hand, trivalent In3+ is more suitable as it can completely replace Y3+ since it can both serve as a point defect source and increase acidity of the crystal lattice. Because of these properties it can be introduced in much larger amounts than Nb5+ or Ta5+. In this study BaCe0.9-xNbxY0.1O3-δ (where x = 0.01, 0.03 and 0.05) and BaCe1-xInxO3-δ (where x = 0.15, 0.20 and 0.25) powders were synthesized by the method of autocombustion, while BaCe0.9-xTaxY0.1O3-δ (where x = 0.01, 0.03 and 0.05) powders were prepared by the classical solid state route. Much higher specific surface areas were observed for the samples synthesized by the autocombustion method. In the case of Nb and Ta doped samples, the dense electrolytes were formed after sintering at 1550 ºC for 5 h in air. Temperature of 1300 ºC was enough to complete sintering of the samples doped with In after 5 h in air, which was another advantage of In as a dopant. The conductivities determined by impedance measurements in temperature range of 550-700 ºC in wet hydrogen showed a decreasing trend with increase of Nb and Ta content, while it was the opposite in the case of In. Interestingly, the total conductivity of the samples BaCe0.85Nb0.05Y0.1O3-δ, BaCe0.85Ta0.05Y0.1O3-δ and BaCe0.75In0.25O3-δ reached around 5×10–3 S/cm in wet hydrogen atmosphere at 700 ºC. After exposure in 100 % CO2 atmosphere at 700 ºC for 5 h, the samples were investigated by X-ray analysis. It was found that even 15 % In could completely supress degradation of electrolyte, while the highest concentrations of Nb and Ta (5%) were necessary to secure sufficient stability in CO2

Solid state synthesis of extra phase-pure Li4Ti5O12 spinel

Extra phase-pure Li4Ti5O12 spinel with particle sizes less than 500 nm was synthesized by solid state reaction of mechanochemicaly activated mixture of nano anatase and Li2CO3 for a very short annealing time, 4 h at 800°C. Structural and microstructural properties, the mechanism of solid state reaction between anatase and Li2CO3 as well as thermal stability of prepared spinel were investigated using XRPD, SEM and TG/DSC analysis. The mechanism of reaction implies decomposition of Li2CO3 below 250ºC, formation of monoclinic Li2TiO3 as intermediate product between 400 and 600°C and its transformation to Li4Ti5O12 between 600-800ºC. The spinel structure is stable up to 1000ºC when it is decomposed due to Li2O evaporation

Effect of conjugated linoleic acid in the diet on performance and meat quality of broilers

Osnovni cilj istraživanja u okviru ove doktorske disertacije je bio da se ispita uticaj konjugovane linolne kiseline (conjugated linoleic acid-CLA) na proizvodne rezultate (potrošnja hrane, prirast, konverzija), parametre mesnatosti (pocenat mesa u trupu) i kvalitet mesa brojlera (hemijski sastav, senzorne osobine, masnokiselinski sastav, uključujući sadržaj CLA, sadržaj malondialdehida). Za ogled su korišćeni brojleri Cobb 500 provenijencije podeljeni u četiri grupe po 30 životinja i hranjeni standardnim smešama po preporuci proizvođača, s tim što su se grupe razlikovale jedino u tome što su ogledne grupe imale u obroku dodat komercijalni preparat konjugovane kiseline, u preporučenoj količini od 2% u smeši u različitim fazama tova (O-I grupa 2% CLA od početka tova, O-II grupa 2% CLA od 11. dana tova, O-III grupa 2% CLA od 22. dana tova) i kontrolna grupa (K grupa) bez dodatka CLA. Smeše su bile izbalansirane i u potpunosti zadovoljavale potrebe životinja u svim fazama tova. Na kraju tova životinje su izmerene, izračunata je potrošena količina hrane, a na klanici uzeti uzorci masnog tkiva i mesa za hemijske analze (hemijski sastav mesa, MDA i masnokiselinski sastav) i senzorne analize. Uzorci mesa bataka sa karabatakom za određivanje sadržaja MDA zamrznuti su pri -18oC. Na klanici su posle rasecanja izmerene mase osnovnih delova (grudi, batak sa karabatakom) trupa. Kod izoenergetskih i izoproteinskih smeša za ishranu brojlera utvrđene su statistički značajne razlike između prosečnih sadržaja zasićenih, mononezasićenih, polinezasićenih, n-3 i n-6 masnih kiselina. Utvrđena je statistički značajna razlika između odnosa n-3 i n-6 masnih kiselina. Prosečan ukupan sadržaj konjugovane linolne kiseline u smeši za ishranu oglednih grupa brojlera bio je 4,43 %. U hrani za kontrolnu grupu brojlera nije utvrđeno prisustvo konjugovane linolne kiseline. Na početku tova, a zatim na kraju prve i druge faze tova, kao i na kraju tova nisu utvrđene statistički značajne razlike između prosečnih masa ispitivanih grupa brojlera. Prosečan prirast za ceo period tova bio je najveći kod O-I grupe a najmanji kod K grupe brojlera, dok je ukupna konzumacija bila najveća kod K grupe a najmanja kod O-I grupe. Konverzija hrane bila je najbolja kod O-I grupe a najlošija kod kontrolne grupe brojlera. Prosečne mase trupova pre i posle hlađenja, zatim prosečne mase grudi i prosečne mase bataka sa karabatakom kao i njihova zastupljenost u masi trupa nisu se statistički značajno razlikovale između poređenih grupa brojlera. Takođe nije utvrđena statistički značajna razlika između prosečnih masa, odnosno učešća mesa u grudima, odnosno bataku sa karabatakom ispitivanih grupa brojlera. Između prosečnih pH vrednosti, odnosno prosečnih temperatura mesa merenih nakon 45 minuta, odnosno posle 24 sata od klanja nisu utvrđene statistički značajne razlike...The main objective of research under this doctoral thesis was to investigate the influence of conjugated linoleic acid (CLA) on performance (feed consumption, weight gain, conversion), the parameters of leanness (pocenat meat in the carcass) and meat quality of broilers (chemical composition, sensory characteristics, fatty acid composition including the content of CLA and content of malondialdehyde). For the experiment used broilers Cobb 500 provenience divided into four groups of 30 animals and fed standard diets as recommended by the manufacturer, provided that the groups differed only in the fact that the experimental group had a meal added to a commercial preparation of conjugated acid, the recommended amount of 2% in the mixture at different stages of production (O-I group 2% CLA since the beginning of the fattening period, O-II group 2% CLA of 11. days of fattening, O-III group 2% CLA of 22.days of fattening) and control (K group) without the addition of CLA. Mixtures were balanced and fully meet the needs of animals in all stages of this. At the end of fattening animals are weighed, calculated the amount of food consumed, and at the slaughterhouse sampled fat and meat for chemical analze (chemical composition of meat MDA and fatty acid composition) and sensory analysis. Samples of drumstick with thigh for determination of MDA were frozen at -18°C. At the slaughterhouse, the meat preservation after the measured weight of the basic parts (breast, drumstickwith thigh) carcass. In meal for broilers, balanced on the energy and protein content,were found statistically significant differences between average content of saturated, monounsaturated, polyunsaturated, n-3 and n-6 fatty acids. There was a statistically significant difference between the ratios of n-3 and n-6 fatty acids. Average total content of conjugated linoleic acid in the mixture for feeding experimental group of broilers was 4.43%. The feed of the control group was not detected conjugated linoleic acid. At the beginning of this, and then at the end of the first and second phases of fattening, as at the end of fattening there were no statistically significant differences between the average mass of examined groups of broilers. Average growth for the whole fattening period was highest in O-I group and the lowest in K group of broilers, while the total consumption was highest in K group and the lowest in O-I group. Feed conversion was the best in O-I group and the worst in the control group of chickens. Average carcass weight before and after cooling, then the average breast weight and the average weight of drumsticks with thighs as well as their representation in carcass weight did not significantly differ between the examined groups of broilers. There was also no statistically significant difference between the average weight and participation in breast meat and drumsticks with thighs examined groups of broilers. Between average pH value and the average temperature of meat measured after 45 minutes and after 24 hours of slaughter were no statistically significant differences..

Cross-cultural comparison of the Benign and Malicious Envy Scale (BeMaS) across Serbian and US samples and further validation

The aim of this research was to validate the dual conception of envy in Serbian culture, measured by the Benign and Malicious Envy Scale (BeMaS). In Study 1 (N = 404), the results confirmed cross-cultural invariance of the Malicious Envy scale across Serbian and US samples, with the US sample obtaining higher scores. However, two items in the Benign Envy scale showed significant differential item functioning across samples. Nonetheless, both scales in Serbian showed adequate measurement precision (information) and the expected distinction in relations with narcissistic admiration, narcissistic rivalry, and self-esteem, with more aversive characteristics associated with Malicious Envy. In Study 2 (N = 404), Malicious Envy showed a negative relation with Conscientiousness and Openness, as well as higher negative correlations with Honesty-Humility, Agreeableness, psychopathy, and sadism compared to Benign Envy. Furthermore, Malicious Envy showed higher positive correlations with psychological distress, while Benign Envy showed negative correlations with some aspects of distress. The results support good psychometric properties of BeMaS scores of the Serbian adaptation and add to the cross-cultural validity of the dual conception of envy

METROPOLITAN MIHAILO (JOVANOVIĆ) AND PROVINCES OF BOSNIA AND HERZEGOVINA

The authors of this article examine the relations of Metropolitan Mihailo (Jovanović) of Belgrade with the provinces of Bosnia and Herzegovina.  Recognizing the fact that the Metropolitan was supportive for the idea of liberation of all Serbs from Ottoman rule and their unification in one single nation state, the Ottoman ruled provinces of Bosnia and Herzegovina were, without exception, the focus of his attention and actions. He especially proved this during the Serb uprisings in the periods 1852–1862, 1875–1878 and in 1882.  Politically, the Metropolitan supported co-operation with Russia. As such his determination in the period when Serbia was relying on Austro-Hungary caused him difficulties, resulting in his dismissal in 1881. After return to Serbia he was reappointed as Metropolitan in 1889 and continued his work for nationhood, but did so by paying attention to Old Serbia and Macedonia rather than to the provinces of Bosnia and Herzegovina

METROPOLITAN MIHAILO (JOVANOVIĆ) AND PROVINCES OF BOSNIA AND HERZEGOVINA

The authors of this article examine the relations of Metropolitan Mihailo (Jovanović) of Belgrade with the provinces of Bosnia and Herzegovina.  Recognizing the fact that the Metropolitan was supportive for the idea of liberation of all Serbs from Ottoman rule and their unification in one single nation state, the Ottoman ruled provinces of Bosnia and Herzegovina were, without exception, the focus of his attention and actions. He especially proved this during the Serb uprisings in the periods 1852–1862, 1875–1878 and in 1882.  Politically, the Metropolitan supported co-operation with Russia. As such his determination in the period when Serbia was relying on Austro-Hungary caused him difficulties, resulting in his dismissal in 1881. After return to Serbia he was reappointed as Metropolitan in 1889 and continued his work for nationhood, but did so by paying attention to Old Serbia and Macedonia rather than to the provinces of Bosnia and Herzegovina

Some parameters of dried pork produced with lower salt content

Production of meat products with lower salt/sodium content is the goal of today's meat industry because of bad influence of exceed sodium intake by food. In this paper are presented some physico-chemical parameters during processing of dried pork produced with lower salt content. Pork (m. longissimus dorsi) was cured with nitrite curing salt in amount of 3 kg/100 kg of meat. In meat were measured the weight loss during curing and drying; moisture content by standard method SRPS ISO 1442:1998, water activity using awmeter (Wert-Messer, Durotherm) at temperature of 25°C; and pH value by pH-meter (MA-5730; PAT N° 35398, Iskra) according to SRPS ISO 29 17:2004. Average moisture content in dried meat at the end of production was 40.10%. Average weight loss was 2.39% after 7 days of production (after curing) and it is increased up to the end of production, average 34.57%. Acidity of meat during curing, smoking and drying was similar; pH value was around 6.00. Water activity was gradually decreased from average 0.985 after curing (7th day) up to 0.899 at the end of production. During the storage of dried meat under vacuum conditions, pH value decreased from 5.43 in the final product up to 5.11 at the end of storage (120th day). These values are characteristic for curing, drying and fermentation of meat. Dried meat was shelf stable for 120 day under vacuum conditions, without signs of rancidity and without changes in other sensory attributes