Radovan Omorjan

Electrical conductivity of sol-gel derived yttria-stabilized zirconia

A 3 mol% Y2O3 zirconia stabilized powder has been synthesized by destabilization of an aqueous zirconia sol prepared by the alkoxide hydrolysis method. The powder calcined at 500°C is ultrafine with tetragonal crystallites of about 8 nm, slightly agglomerated and with a narrow pore size distribution having an average pore size of 5.2 nm. Zirconia ceramics with density higher than 92%TD and grain size on the order of 100 nm have been obtained by uniaxial pressing at 500 MPa and vacuum sintering at 1000°C. Electrical conductivity of sintered samples, evaluated by complex impedance spectroscopy measurements, indicated that the zirconia stabilized with 3 mol% Y2O3 can potentially be used as an oxygen semipermeable dense membrane, but only at a relatively high temperature.

Sequence polymorphism of the mitochondrial DNA control region in the population of Vojvodina Province, Serbia

In order to generate and establish the database for forensic identification purposes in Vojvodina Province (Serbia), the sequence of the hypervariable regions 1 (HV1) and 2 (HV2) of the mtDNA control region were determined in a population of 104 unrelated individuals from Vojvodina Province, using a fluorescent-based capillary electrophoresis sequencing method. A total of 93 different haplotypes were found, of these 83 mtDNA types were unique, nine haplotypes were shared by two individuals and one haplotype by three individuals. The variation of mtDNA HV1 and HV2 regions was confined to 116 nucleotide positions, of which 72 were observed in the HV1 and 44 in the HV2. A statistical estimate of the results for this population showed the genetic diversity of 0.9977 and the random match probability of 1.18%. Haplogroup H was the most common haplogroup (43.3%). Haplogroups observed at intermediate levels included clusters U (13.5%), T (10.6%), J (8.6%) and W (5.8%).

Pectinase partitioning in polyethylene glycol 1000/Na2SO4 aqueous two-phase system: statistical modeling of the experimental results

Statistical models concerning partitioning of pectinase in polyethylene glycol 1000/Na2SO4 aqueous two-phase system were established with response surface methodology. Concentrations of polyethylene glycol 1000 and Na2SO4 were selected as independent variables to evaluate their impact on parameters of partitioning in aqueous two-phase system—the partition coefficient of pectinase, purification factor and pectinase yield. An experimental space where over 2.5-fold purification was achieved, followed by over 90% yield of pectinase. The established models showed good prediction of partitioning parameters.

Influence of combined emulsifier on physical characteristics of fat filling

The influence of mixture of two separate emulsifiers and a new generation of emulsifier 2 in 1, which nowadays has a tendency to replace these two, on the rheological and textural properties and sensory quality of fat filling was investigated. Emulsifiers were added in concentrations of 0.3, 0.45 and 0.75%, and calculated on the total mass of raw materials. The addition of emulsifiers in concentrations of 0.3 and 0.45% had a significant influence on the textural and rheological parameters of fat filling. These results showed that is not necessary to add a maximum amount of an emulsifier in order to achieve optimal spreadibility and hardness, which is certainly justified from an economic point of view. The addition of emulsifier 2 in 1 caused starchy taste and migration of fat to the surface of fat filling. The sample with 0.45%, which was a combination of two emulsifiers, had the best sensory quality and spreadability characteristics.